fix(android): gate the latency overhaul behind an experimental toggle, default off

The 27c53a4 low-latency overhaul regressed badly on some phones. Every piece
of it — decoder ranking, per-SoC vendor keys, the async decode loop, pipeline
thread boosts, the ADPF max-performance bias, game-tagged AAudio, DSCP marking,
the Wi-Fi low-latency lock, HDMI ALLM and the forced TV mode switch — now rides
the "Low-latency mode (experimental)" toggle, default OFF. Off restores the
pre-overhaul pipeline byte-for-byte: the sync poll loop, the platform-default
decoder, and the original format keys (standard low-latency + blind Qualcomm
twin + priority=0 + operating-rate=MAX together).

- New pref key (low_latency_mode_experimental): the old key shipped default-ON,
  so any install that ever saved settings persisted true — flipping the default
  under the old key would leave exactly the regressed devices stuck on.
- DSCP is applied at socket creation, so the toggle reaches the transport via
  NativeBridge.nativeSetLowLatencyMode → transport::set_dscp_default, called in
  the connect choke point before nativeConnect; the core DSCP default reverts
  to off everywhere.
- nativeStartAudio(handle, lowLatencyMode) gates AAudio usage=Game.
- VideoDecoders.pickDecoder now skips `.secure` decoder twins and decoders that
  require FEATURE_SecurePlayback: they need a secure surface, and a secure twin
  could out-score its plain sibling (only it advertising FEATURE_LowLatency),
  which black-screens a clear stream.

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

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

@@ -123,6 +123,15 @@ object NativeBridge {
      */
     external fun nativeWakeOnLan(macsCsv: String, lastIp: String): Boolean
 
+    /**
+     * Apply the user's "Low-latency mode (experimental)" toggle to the process-wide transport
+     * defaults — today just DSCP/QoS marking on the media sockets. Must be called BEFORE
+     * [nativeConnect] (the tag is applied at socket creation); `HostConnect.connectToHost` does.
+     * The rest of the toggle rides explicit per-session parameters ([nativeStartVideo] /
+     * [nativeStartAudio]). Cheap (one atomic store); UI-safe.
+     */
+    external fun nativeSetLowLatencyMode(enabled: Boolean)
+
     /**
      * The MediaCodec MIME the host resolved for this session (`"video/hevc"` / `"video/avc"` /
      * `"video/av01"`), or `""` on a `0` handle. Kotlin ranks `MediaCodecList` decoders for this
@@ -134,10 +143,12 @@ object NativeBridge {
      * Start the decode thread rendering onto [surface] (a SurfaceView's surface). Decode runs
      * entirely in Rust (NDK AMediaCodec → ANativeWindow) — no per-frame JNI. [decoderName] is the
      * decoder Kotlin ranked from `MediaCodecList` (`""` = let the platform resolve the default for
-     * the MIME); [lowLatencyMode] is the user's master toggle (default on → aggressive per-SoC
-     * tuning; off → conservative); [lowLatencyFeature] is whether [decoderName] advertised
-     * `FEATURE_LowLatency` (HUD label only). [isTv] drives an active HDMI mode switch to the stream
-     * refresh on TV boxes (vs. the softer seamless hint on phones). No-op if already started.
+     * the MIME — what the pre-overhaul client always did); [lowLatencyMode] is the user's
+     * "Low-latency mode (experimental)" toggle (off, the default, runs the original decode
+     * pipeline; on, the aggressive per-SoC tuning + async loop); [lowLatencyFeature] is whether
+     * [decoderName] advertised `FEATURE_LowLatency` (HUD label only). [isTv] drives an active HDMI
+     * mode switch to the stream refresh on TV boxes when the toggle is on (vs. the softer seamless
+     * hint otherwise). No-op if already started.
      */
     external fun nativeStartVideo(
         handle: Long,
@@ -183,10 +194,12 @@ object NativeBridge {
     external fun nativeSetVideoStatsEnabled(handle: Long, enabled: Boolean)
 
     /**
-     * Start host→client audio: Opus decode → jitter ring → AAudio (LowLatency), all in Rust. No-op
-     * if already started. Best-effort — a failure leaves video streaming.
+     * Start host→client audio: Opus decode → jitter ring → AAudio (LowLatency), all in Rust.
+     * [lowLatencyMode] (the experimental toggle) additionally tags the stream usage=Game for the
+     * HAL's game-audio routing. No-op if already started. Best-effort — a failure leaves video
+     * streaming.
      */
-    external fun nativeStartAudio(handle: Long)
+    external fun nativeStartAudio(handle: Long, lowLatencyMode: Boolean)
 
     /** Stop + join the audio thread and close AAudio, without closing the session. No-op on `0`. */
     external fun nativeStopAudio(handle: Long)

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

@@ -57,7 +57,17 @@ object VideoDecoders {
             val name = info.name
             val lower = name.lowercase()
             if (BLOCKED_PREFIXES.any { lower.startsWith(it) } || lower in BLOCKED_EXACT) continue
+            // Never a secure decoder: `.secure` names are the DRM-pipeline twins of the real
+            // decoder and require a secure surface — configuring one for a clear stream fails (or
+            // renders black). The plain twin is also in the list, so drop rather than rank
+            // (a `.secure` twin can otherwise OUT-score its plain sibling when only it advertises
+            // FEATURE_LowLatency). Moonlight filters the same way.
+            if (lower.endsWith(".secure")) continue
             val caps = runCatching { info.getCapabilitiesForType(mime) }.getOrNull() ?: continue
+            val secureRequired = runCatching {
+                caps.isFeatureRequired(CodecCapabilities.FEATURE_SecurePlayback)
+            }.getOrDefault(false)
+            if (secureRequired) continue
 
             val hardware = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
                 info.isHardwareAccelerated