docs: repo-wide housekeeping — sync README & docs with the code as shipped

Six parallel audits swept the root docs, docs-site, every per-directory
README, and the packaging docs; every claim below was verified against
the source before editing.

- README: Layout gains the six missing crates (pf-client-core,
  pf-presenter, pf-console-ui, pf-ffvk, pf-driver-proto, punktfunk-tray),
  clients/session, api/ and ci/; Linux/Windows client rows reflect the
  shell + Vulkan-session split and the Vulkan Video -> VAAPI/D3D11VA ->
  software decode chains; the "every client over a C ABI" claim is
  corrected (Rust clients link the core directly); tiered stats overlay
  + console shell noted; Apple row mentions AV1.
- CONTRIBUTING: drop the dead CLAUDE.md link (deliberately untracked);
  point at the README's build/invariants sections. SECURITY: 0.9.0.
- host-cli/pairing: --allow-pairing/--require-pairing are no-op legacy
  names — pairing is required by default, --allow-tofu is the real flag;
  document --data-port and --idle-timeout-ms.
- configuration: document PUNKTFUNK_RECOVER_SESSION_CMD (session-crash
  recovery hook), PUNKTFUNK_MDNS, PUNKTFUNK_DATA_PORT.
- virtual-displays/gnome: GNOME per-client scaling shipped (host-
  persisted) — flip the ❌ to ✅ and describe how it works.
- stats: new "Detail levels" section (Off/Compact/Normal/Detailed +
  per-platform cycle gestures); retire the GTK hand-off note.
- clients/install-client/status/roadmap: decode chains, Windows client
  validation narrowed to HDR-only pending, adaptive bitrate, console
  shell, Apple AV1, Windows host vendor list.
- Sub-READMEs: clients/linux rewritten for the re-architecture; session
  Windows decode rung + d3d11va knob; Windows tiered overlay; Android
  minSdk 28; decky file table; host zerocopy/ path; scripts port
  47992 and steamos-host.md; pf-dualsense source path.
- packaging: canary version bases are tag-derived (<next-minor> via
  pf-version.sh/.ps1), codecs-extra not ffmpeg-full, document the
  pinned offline-Skia tarball + SKIA_BINARIES_URL and vulkan-headers.
- Convert 15 dangling design/*.md links to the punktfunk-planning
  prose convention (those docs live in the private planning repo).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

crates/punktfunk-core/README.md

@@ -57,5 +57,5 @@ bash crates/punktfunk-core/tests/c/run.sh    # standalone C-ABI link + round-tri
 
 - **[`punktfunk-host`](../punktfunk-host/README.md)** — the streaming host built on this core
 - **[Clients](../../clients/)** — the apps that link this core over the C ABI (or directly, in Rust)
-- **[`design/implementation-plan.md`](../../design/implementation-plan.md)** — why GF(2¹⁶) FEC, the
+- **punktfunk-planning: `implementation-plan.md`** (internal planning repo) — why GF(2¹⁶) FEC, the
   latency budget, and the architecture thesis