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/apple/Sources/PunktfunkClient/Session/SessionModel.swift

@@ -194,9 +194,10 @@ final class SessionModel: ObservableObject {
             if want444, canDecode444 {
                 videoCaps |= PunktfunkConnection.videoCap444
             }
-            // This client's VideoToolbox path decodes H.264 and HEVC (AV1 isn't wired — hosts don't
-            // emit it on the native path yet). The host resolves the emitted codec from these + the
-            // soft `preferredCodec`; `resolvedCodec` reflects what it chose.
+            // This client's VideoToolbox path decodes H.264 and HEVC (AV1 depacketization isn't
+            // wired — AnnexB.swift is NAL-only — so it must never be advertised here). The host
+            // resolves the emitted codec from these + the soft `preferredCodec`; `resolvedCodec`
+            // reflects what it chose.
             let videoCodecs = PunktfunkConnection.codecH264 | PunktfunkConnection.codecHEVC
             let result = Result { try PunktfunkConnection(
                 host: host.address, port: host.port,

clients/apple/Sources/PunktfunkClient/Settings/SettingsOptions.swift

@@ -38,8 +38,8 @@ enum SettingsOptions {
         HUDPlacement.allCases.map { ($0.label, $0.rawValue) }
 
     /// Video-codec preference (`DefaultsKey.codec`) — a soft preference the host falls back from.
-    /// No AV1: this client's VideoToolbox path decodes H.264/HEVC only (hosts don't emit AV1 on
-    /// the native path yet).
+    /// No AV1: this client's VideoToolbox path decodes H.264/HEVC only (AnnexB.swift is NAL-only),
+    /// so it never advertises AV1 — offering it here would be a dead setting.
     static let codecs: [(label: String, tag: String)] = [
         ("Automatic", "auto"),
         ("HEVC (H.265)", "hevc"),