feat(codec): make client codec selection real — GPU-aware native advertisement

The clients' codec pickers sent a preference the host threw away:
host_wire_caps() hardcoded HEVC for every GPU backend, so the native
path never emitted H.264/AV1 regardless of what the user chose.

Host: advertise what the backend actually encodes, mirroring the
GameStream serverinfo logic — software openh264 emits H.264; probed
backends (Linux VAAPI, Windows AMF/QSV) advertise their per-GPU
CodecSupport via the new wire_mask(); NVENC keeps the
Moonlight-validated H.264|HEVC|AV1 static superset; an empty probe
falls back to the superset so auto clients still resolve HEVC. Gate
10-bit to HEVC (like the 4:4:4 gate) now that a client can steer the
codec — Main10 is the only 10-bit encode path. Fix the web-console
stats label hardcoded to "hevc" (new Codec::label(), shared with the
GameStream register_session mapping).

Android: replace the hardcoded H264|HEVC Hello advertisement with a
videoCodecs param fed by VideoDecoders.decodableCodecBits() (AV1 bit
only when a real hardware video/av01 decoder exists — the decode loop
was already mime-driven); offer AV1 in the codec picker on capable
devices.

Decky: add the missing "Video codec" dropdown (auto/hevc/h264/av1) to
the plugin settings, round-tripping the same codec key the flatpak
client reads.

Apple: unchanged by design (AnnexB.swift is NAL-only, AV1 is never
advertised); refresh the stale "hosts don't emit AV1 on the native
path yet" comments here and host-side.

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

clients/android/kit/src/main/kotlin/io/unom/punktfunk/kit/NativeBridge.kt

@@ -48,6 +48,9 @@ object NativeBridge {
         gamepadPref: Int,
         hdrEnabled: Boolean,
         audioChannels: Int,
+        /** `quic::CODEC_*` bitfield of codecs this device decodes ([VideoDecoders.decodableCodecBits]);
+         *  `0` falls back to H.264|HEVC. The host resolves the emitted codec from this ∩ its GPU. */
+        videoCodecs: Int,
         /** Preferred video codec as a `quic::CODEC_*` bit (`0` = auto). Soft — the host falls back. */
         preferredCodec: Int,
         timeoutMs: Int,

clients/android/kit/src/main/kotlin/io/unom/punktfunk/kit/VideoDecoders.kt

@@ -44,6 +44,15 @@ object VideoDecoders {
      * Pick the best decoder for [mime] (`"video/hevc"` / `"video/avc"` / `"video/av01"`), or `null`
      * to let the platform resolve its default. Enumerates once — call at stream start.
      */
+    /**
+     * The `quic::CODEC_*` bitfield of codecs this device can decode, advertised in the Hello so the
+     * host never emits a codec the decode loop can't open: H.264 (1) and HEVC (2) always (universal
+     * on Android hardware), plus AV1 (4) only when [pickDecoder] finds a real (hardware, non-blocked)
+     * `video/av01` decoder. Enumerates `MediaCodecList` — call at connect time, not per frame.
+     */
+    fun decodableCodecBits(): Int =
+        1 or 2 or (if (pickDecoder("video/av01") != null) 4 else 0)
+
     fun pickDecoder(mime: String): DecoderChoice? {
         if (mime.isEmpty()) return null
         val infos = runCatching { MediaCodecList(MediaCodecList.REGULAR_CODECS).codecInfos }