feat(protocol,clients): codec preference negotiation + Linux client decodes per Welcome (Phase 2a)

Adds a client-selectable **preferred codec** and wires the core + ABI + probe + Linux client to
negotiate and decode it. (Windows/Apple/Android follow in 2b.)

**Core:**
- `Hello.preferred_codec` (a single CODEC_* bit, 0 = auto) — a soft hint appended after
  `video_codecs`. `resolve_codec(client, host, preferred)` now honors the preference when the host
  can also emit it, else falls back to precedence (HEVC > AV1 > H.264). Roundtrip + preference tests.
- `NativeClient::connect` takes `video_codecs` + `preferred_codec`; `NativeClient.codec` exposes the
  resolved `Welcome.codec`.
- ABI: `punktfunk_connect_ex7` (adds the two codec params; `ex6` delegates to it advertising
  HEVC-only) + `punktfunk_connection_codec` getter + `PUNKTFUNK_CODEC_{H264,HEVC,AV1}` constants
  (drift-guarded against the wire values). Header regenerated.

**Host:** passes `hello.preferred_codec` into `resolve_codec`.

**probe:** `--codec h264|hevc|av1|auto` sets the preference (still advertises it can decode all
three); the dump extension already follows the resolved codec.

**Linux client:** advertises the codecs FFmpeg can actually decode (`decodable_codecs()`), threads
the user's `codec` setting as the preference, and builds the decoder — both the software and VAAPI
paths, plus the mid-session VAAPI→software demotion — from the negotiated `Welcome.codec` instead of
hardcoding HEVC. New "Video codec" dropdown in Preferences (Automatic/HEVC/H.264/AV1).

Live-validated on the dev box: probe `--codec hevc` against a software (H.264-only) host resolves to
H.264 (graceful soft-preference fallback), no failure. clippy + core (57) + host (133) tests green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

scripts/steamdeck/README.md

@@ -39,9 +39,13 @@ git clone https://git.unom.io/unom/punktfunk ~/punktfunk
 bash ~/punktfunk/scripts/steamdeck/install.sh            # PIN pairing required (secure default)
 bash ~/punktfunk/scripts/steamdeck/install.sh --open     # trusted LAN: accept unpaired clients
 bash ~/punktfunk/scripts/steamdeck/install.sh --no-web   # host only, no web console
+bash ~/punktfunk/scripts/steamdeck/install.sh --no-gamestream  # native punktfunk/1 only, no Moonlight surface
 bash ~/punktfunk/scripts/steamdeck/update.sh             # after pulling new source
 ```
 
+Note: unlike a bare `serve` (native-only by default), the Deck install enables `--gamestream` by
+default so stock Moonlight clients work out of the box; `--no-gamestream` turns that surface off.
+
 Env overrides: `PUNKTFUNK_SRC` (source dir, default `~/punktfunk`), `PUNKTFUNK_BOX` (container name,
 default `pf2`), `PUNKTFUNK_MGMT_PORT` (47990), `PUNKTFUNK_WEB_PORT` (3000).
 

scripts/windows/README.md

@@ -36,7 +36,7 @@ won't start. The service is down only for the build duration.
 
 On an **installed** host (the `setup.exe`) the console is set up automatically — no manual steps.
 The installer bundles the built (self-contained, no-`node_modules`) `.output` server + a portable
-bun and runs `scripts\windows\web-setup.ps1`, which registers the **`PunktfunkWeb`** scheduled task
+bun and runs `punktfunk-host.exe web setup`, which registers the **`PunktfunkWeb`** scheduled task
 (at boot, as SYSTEM, restart-on-failure) running `{app}\web\web-run.cmd` →
 `bun …\.output\server\index.mjs` on `:3000`, opens inbound TCP 3000, and writes the login password to
 `%ProgramData%\punktfunk\web-password` (ACL'd to Administrators + SYSTEM). The mgmt bearer token it
@@ -52,8 +52,8 @@ powershell -ExecutionPolicy Bypass -File scripts\windows\build-web.ps1
 
 `bun install && bun run build` (Nitro `noExternals` -> a self-contained `.output`, no
 `node_modules`/`.npmrc`), then restarts the `PunktfunkWeb` task and checks `:3000/login`. Use
-this to iterate on the console against an installed host - `web-setup.ps1` (or a fresh install) is
-what creates the task in the first place.
+this to iterate on the console against an installed host - `punktfunk-host.exe web setup` (or a
+fresh install) is what creates the task in the first place.
 
 ## Typical flow after pulling new code