feat(theme): add site footer and marketing sections

- Add SiteFooter, rendered through the Layout bottom slot so it appears on
  every page type. themeConfig.footer is deliberately left unset: setting
  it would render the built-in HomeFooter as well, on the home page only.
- Add a frontmatter-driven section system (advantages, contentGrid,
  techStack, cases and cta) with a single ordered array, so bands can be
  reordered or removed without touching code.
- Bands render only when they have content, so an unfilled page degrades
  to its heading rather than showing empty boxes.
- Add a SHOW_COPY_PLACEHOLDERS flag for drafting, false by default.

theme/components/sections/CallToAction.tsx

@@ -0,0 +1,67 @@
+import { Button } from "@rspress/core/theme-original"
+import { arr, str, type CallToActionLink, type ContactCode } from "./types"
+
+/**
+ * Closing call-to-action band: one or more buttons, optionally alongside a
+ * scannable contact code (a WeChat QR, for instance).
+ *
+ * `Button` renders its own `<a>` (routed through the theme's `Link`), so it
+ * must be given `href` directly rather than being wrapped in an anchor.
+ */
+export function CallToAction({
+  actions,
+  code,
+}: {
+  actions?: CallToActionLink[]
+  code?: ContactCode
+}) {
+  const links = (arr<CallToActionLink>(actions) ?? []).filter(
+    (action) => str(action?.text) && str(action?.link)
+  )
+  const codeSrc = str(code?.src)
+  const codeCaption = str(code?.caption)
+
+  if (links.length === 0 && !codeSrc) return null
+
+  return (
+    <div className="flex flex-col items-center gap-8">
+      {links.length > 0 && (
+        <div className="flex flex-wrap justify-center gap-4">
+          {links.map((action, index) => (
+            <Button
+              key={`${str(action.text)}-${index}`}
+              type="a"
+              theme={action.theme === "alt" ? "alt" : "brand"}
+              href={str(action.link) as string}
+              // `.rp-button--big` sets a min-width but no horizontal padding, so
+              // a long label such as an email address runs into the rounded
+              // edges. Supply the padding ourselves.
+              className="px-10">
+              {str(action.text)}
+            </Button>
+          ))}
+        </div>
+      )}
+
+      {codeSrc && (
+        <figure className="m-0 flex flex-col items-center gap-3">
+          {/* The white frame is not decoration. A QR code needs a quiet zone of
+              blank space around it to scan reliably, and the exported image has
+              almost none — the pattern runs close to its edges. */}
+          <div className="rounded-xl border border-(--rp-c-divider-light) bg-white p-4">
+            <img
+              src={codeSrc}
+              alt={codeCaption ?? ""}
+              width={160}
+              height={160}
+              className="block h-40 w-40"
+            />
+          </div>
+          {codeCaption && (
+            <figcaption className="text-sm text-(--rp-c-text-2)">{codeCaption}</figcaption>
+          )}
+        </figure>
+      )}
+    </div>
+  )
+}

theme/components/sections/Cases.tsx

@@ -0,0 +1,102 @@
+import { useCallback, useEffect, useState } from "react"
+import { arr, str, type CaseStudy } from "./types"
+
+const ROTATE_MS = 8000
+
+/**
+ * Customer case-study carousel.
+ *
+ * TODO(copy): populate `frontmatter.sections` with real case studies. With no
+ * items this renders nothing; with exactly one it degrades to a static card.
+ *
+ * Rotation is suspended when the visitor prefers reduced motion, and pauses
+ * while the carousel is hovered or focused.
+ */
+export function Cases({ items }: { items?: CaseStudy[] }) {
+  const studies = (arr<CaseStudy>(items) ?? []).filter((item) => str(item?.company))
+  const [active, setActive] = useState(0)
+  const [paused, setPaused] = useState(false)
+
+  const count = studies.length
+  const go = useCallback(
+    (next: number) => setActive(count > 0 ? ((next % count) + count) % count : 0),
+    [count]
+  )
+
+  useEffect(() => {
+    if (count <= 1 || paused) return
+    if (
+      typeof window !== "undefined" &&
+      window.matchMedia?.("(prefers-reduced-motion: reduce)").matches
+    ) {
+      return
+    }
+    const timer = window.setInterval(() => setActive((current) => (current + 1) % count), ROTATE_MS)
+    return () => window.clearInterval(timer)
+  }, [count, paused])
+
+  if (count === 0) return null
+
+  const current = studies[Math.min(active, count - 1)]
+  const company = str(current.company) ?? ""
+  const quote = str(current.quote)
+  const details = str(current.details)
+  const author = str(current.author)
+  const role = str(current.role)
+  const link = str(current.link)
+  const logo = str(current.logo)
+
+  return (
+    <div
+      className="rounded-xl border border-(--rp-c-divider-light) bg-(--rp-c-bg-soft) p-8"
+      onMouseEnter={() => setPaused(true)}
+      onMouseLeave={() => setPaused(false)}
+      onFocus={() => setPaused(true)}
+      onBlur={() => setPaused(false)}>
+      <figure className="m-0 flex flex-col items-center gap-6 text-center">
+        {logo && <img src={logo} alt={company} height={40} className="h-10 w-auto" />}
+        {quote && (
+          <blockquote className="m-0 max-w-3xl text-lg leading-relaxed text-(--rp-c-text-1)">
+            {quote}
+          </blockquote>
+        )}
+        {/* Without an approved testimonial, describe the engagement instead. */}
+        {!quote && details && (
+          <p className="m-0 max-w-2xl text-base leading-relaxed text-(--rp-c-text-1)">{details}</p>
+        )}
+        <figcaption className="text-sm text-(--rp-c-text-2)">
+          {author && <span className="font-medium text-(--rp-c-text-1)">{author}</span>}
+          {author && role && <span> · </span>}
+          {role}
+          {link ? (
+            <>
+              {" · "}
+              <a className="rp-link" href={link}>
+                {company}
+              </a>
+            </>
+          ) : (
+            company && <span> · {company}</span>
+          )}
+        </figcaption>
+      </figure>
+
+      {count > 1 && (
+        <div className="mt-6 flex justify-center gap-2">
+          {studies.map((study, index) => (
+            <button
+              key={`${str(study.company)}-${index}`}
+              type="button"
+              aria-label={str(study.company)}
+              aria-current={index === active}
+              onClick={() => go(index)}
+              className={`h-2 w-2 cursor-pointer rounded-full border-0 p-0 transition-colors ${
+                index === active ? "bg-(--rp-c-brand)" : "bg-(--rp-c-divider)"
+              }`}
+            />
+          ))}
+        </div>
+      )}
+    </div>
+  )
+}

theme/components/sections/FeatureGrid.tsx

@@ -0,0 +1,15 @@
+import type { Feature } from "@rspress/core"
+import { HomeFeature } from "@rspress/core/theme-original"
+import { arr } from "./types"
+
+/**
+ * Card grid used for both the homepage advantages and the products/services
+ * grids. Delegates to the stock `HomeFeature`, which already handles `span`,
+ * icons and the reveal animation — it accepts a `features` prop precisely so it
+ * can be driven from somewhere other than page frontmatter.
+ */
+export function FeatureGrid({ items }: { items?: Feature[] }) {
+  const features = arr<Feature>(items)
+  if (!features) return null
+  return <HomeFeature features={features} />
+}

theme/components/sections/SectionBand.tsx

@@ -0,0 +1,49 @@
+import type { ReactNode } from "react"
+import { SHOW_COPY_PLACEHOLDERS } from "./placeholder"
+import { str, type Section } from "./types"
+
+interface SectionBandProps {
+  section: Section
+  /** Whether the section body produced any content. */
+  hasContent: boolean
+  children: ReactNode
+}
+
+/**
+ * Shell for a marketing band: the `<section>` wrapper, its heading and its
+ * subtitle. Renders nothing at all when the section has neither content nor a
+ * heading, so an unfilled page degrades to just its hero.
+ */
+export function SectionBand({ section, hasContent, children }: SectionBandProps) {
+  const title = str(section.title)
+  const subtitle = str(section.subtitle)
+
+  if (!hasContent && !title && !subtitle) {
+    if (!SHOW_COPY_PLACEHOLDERS) return null
+    return (
+      <section id={section.id} className="rp-site-section">
+        <div className="mx-auto max-w-5xl px-6">
+          <div className="rounded-lg border border-dashed border-(--rp-c-divider) p-8 text-center text-sm text-(--rp-c-text-3)">
+            TODO: {section.type}
+          </div>
+        </div>
+      </section>
+    )
+  }
+
+  return (
+    <section id={section.id} className="rp-site-section">
+      <div className="mx-auto max-w-5xl px-6">
+        {(title || subtitle) && (
+          <header className="mb-10 text-center">
+            {title && <h2 className="m-0 text-3xl font-semibold text-(--rp-c-text-1)">{title}</h2>}
+            {subtitle && (
+              <p className="mx-auto mt-3 max-w-2xl text-base text-(--rp-c-text-2)">{subtitle}</p>
+            )}
+          </header>
+        )}
+        {children}
+      </div>
+    </section>
+  )
+}

theme/components/sections/TechStack.tsx

@@ -0,0 +1,57 @@
+import { arr, str, type TechStackGroup, type TechStackItem } from "./types"
+
+/**
+ * Technology matrix: named groups of technologies, each with an optional
+ * emoji/icon and link.
+ *
+ * TODO(copy): populate `frontmatter.sections` with real entries. Groups with no
+ * items are skipped, so a half-filled list still renders sensibly.
+ */
+export function TechStack({ groups }: { groups?: TechStackGroup[] }) {
+  const visible = (arr<TechStackGroup>(groups) ?? [])
+    .map((group) => ({ group, items: arr<TechStackItem>(group?.items) ?? [] }))
+    .filter(({ items }) => items.length > 0)
+
+  if (visible.length === 0) return null
+
+  return (
+    <div className="flex flex-col gap-10">
+      {visible.map(({ group, items }, groupIndex) => (
+        <div key={str(group.name) ?? `group-${groupIndex}`}>
+          <h3 className="mb-4 text-sm font-semibold uppercase tracking-wide text-(--rp-c-text-3)">
+            {str(group.name) ?? ""}
+          </h3>
+          <ul className="m-0 grid list-none grid-cols-2 gap-3 p-0 sm:grid-cols-3 md:grid-cols-4">
+            {items.map((item, itemIndex) => {
+              const name = str(item?.name)
+              if (!name) return null
+              const url = str(item?.url)
+              const icon = str(item?.icon)
+              const body = (
+                <span className="flex items-center gap-2">
+                  {icon && <span aria-hidden="true">{icon}</span>}
+                  <span>{name}</span>
+                </span>
+              )
+              return (
+                <li key={`${name}-${itemIndex}`} className="m-0">
+                  {url ? (
+                    <a
+                      className="rp-link flex items-center rounded-md border border-(--rp-c-divider-light) px-3 py-2 no-underline transition-colors hover:bg-(--rp-c-bg-mute)"
+                      href={url}>
+                      {body}
+                    </a>
+                  ) : (
+                    <span className="flex items-center rounded-md border border-(--rp-c-divider-light) px-3 py-2">
+                      {body}
+                    </span>
+                  )}
+                </li>
+              )
+            })}
+          </ul>
+        </div>
+      ))}
+    </div>
+  )
+}

theme/components/sections/placeholder.ts

@@ -0,0 +1,11 @@
+/**
+ * Flip to `true` while drafting copy: sections with no content then render a
+ * dashed outline naming their type, instead of collapsing to nothing.
+ *
+ * MUST be `false` before release — confirm this file is the only match:
+ *   grep -rn SHOW_COPY_PLACEHOLDERS theme/
+ *
+ * A plain constant is used rather than `import.meta.env.DEV` because the theme
+ * bundle does not guarantee that variable is inlined.
+ */
+export const SHOW_COPY_PLACEHOLDERS = false

theme/components/sections/types.ts

@@ -0,0 +1,102 @@
+import type { Feature } from "@rspress/core"
+
+/**
+ * Shape of a `frontmatter.sections` entry.
+ *
+ * `FrontMatterMeta` ends with an index signature so `sections` is accepted, but
+ * frontmatter is parsed at runtime by gray-matter and takes no part in MDX type
+ * checking — every field must therefore be defended at the point of use.
+ */
+
+export interface TechStackItem {
+  name: string
+  icon?: string
+  url?: string
+}
+
+export interface TechStackGroup {
+  name: string
+  items?: TechStackItem[]
+}
+
+export interface CaseStudy {
+  company: string
+  logo?: string
+  /** A client testimonial. Only use one the client has actually approved. */
+  quote?: string
+  author?: string
+  role?: string
+  link?: string
+  /**
+   * What the engagement was. Rendered instead of `quote` when there is no
+   * approved testimonial — far better than showing a bare company name.
+   */
+  details?: string
+}
+
+export interface CallToActionLink {
+  theme?: "brand" | "alt"
+  text: string
+  link: string
+}
+
+/** A scannable code, such as a WeChat contact QR. `src` is a public asset path. */
+export interface ContactCode {
+  src: string
+  caption?: string
+}
+
+interface SectionBase {
+  id?: string
+  title?: string
+  subtitle?: string
+}
+
+export type Section =
+  | (SectionBase & { type: "advantages"; items?: Feature[] })
+  | (SectionBase & { type: "contentGrid"; items?: Feature[] })
+  | (SectionBase & { type: "techStack"; groups?: TechStackGroup[] })
+  | (SectionBase & { type: "cases"; items?: CaseStudy[] })
+  | (SectionBase & {
+      type: "cta"
+      actions?: CallToActionLink[]
+      code?: ContactCode
+    })
+
+export type SectionType = Section["type"]
+
+/** Returns a trimmed string, or `undefined` when the value is missing or blank. */
+export function str(value: unknown): string | undefined {
+  return typeof value === "string" && value.trim() ? value.trim() : undefined
+}
+
+/** Returns a non-empty array, or `undefined`. */
+export function arr<T>(value: unknown): T[] | undefined {
+  return Array.isArray(value) && value.length > 0 ? (value as T[]) : undefined
+}
+
+/**
+ * Whether a section would render any body content.
+ *
+ * Shared by the renderers (which return `null` when empty) and by
+ * `SectionBand`, so the two can never disagree about whether a band is empty.
+ */
+export function hasContent(section: Section): boolean {
+  switch (section.type) {
+    case "advantages":
+    case "contentGrid":
+      return arr<Feature>(section.items) !== undefined
+    case "techStack":
+      return (
+        arr<TechStackGroup>(section.groups)?.some(
+          (group) => arr<TechStackItem>(group?.items) !== undefined
+        ) ?? false
+      )
+    case "cases":
+      return arr<CaseStudy>(section.items) !== undefined
+    case "cta":
+      return (
+        arr<CallToActionLink>(section.actions) !== undefined || str(section.code?.src) !== undefined
+      )
+  }
+}