feat(android): a timeline presenter — frames reach glass on the panel's schedule, not decode's

The Android port of the Apple client's stage-4 deadline discipline, closing
the side-by-side feel gap (both clients 120 Hz; Android released decoded
buffers the instant they appeared, with zero vsync awareness — the latch
phase inherited every network+decode jitter and bursts queued behind the
display).

The presenter (async loop only; the sync loop stays the untouched escape
hatch behind the Low-latency toggle):

- decode/vsync.rs: an AChoreographer thread (dlsym'd like the other
  above-floor symbols) publishing the panel's vsync grid + frame timelines
  (postVsyncCallback, API 33; postFrameCallback64 fallback on 31/32) and
  ticking the decode loop's event channel. Started lazily on the first
  decoded frame.
- decode/presenter.rs: a newest-wins slot (Lowest latency, default) or a
  1-3 frame smoothing FIFO with preroll/underflow re-arm (Smoothness) between
  decode and release; a glass budget of exactly ONE undisplayed release in
  flight, reopened at the target timeline's DEADLINE (SurfaceFlinger's latch
  — reopening at present time would halve the sustainable rate) with a 100 ms
  stale force-open backstop; the release itself via
  releaseOutputBufferAtTime(expectedPresent) so the latch phase is
  deterministic. debug.punktfunk.presenter=arrival sysprop restores the
  legacy path for a rebuild-free on-device A/B.
- Metrics: DisplayTracker is now always-on and carries the release stamp, so
  the display stage splits into pace (decoded→release) + latch
  (release→displayed); a 1 Hz pf.present logcat line (released/displays/
  paced/noBudget/forced/qDry + pace/latch p50/max + measured vsync) makes a
  HUD-off wireless A/B readable; nativeVideoStats grows to 30 doubles
  (26=paceP50, 27=latchP50, 28=presents, 29=presenterActive; 0-25 frozen)
  and the DETAILED HUD prints the split + presents.
- Intent parity: present_priority/smooth_buffer — the Apple client's
  stored values and labels — as globals, profile-overlay fields (round-trip
  + scope markers), and Settings pickers under Decoding; threaded through
  nativeStartVideo into the presenter config.

Verified: cargo ndk check/clippy clean for arm64 (the two type_complexity
warnings are pre-existing audio/mic ones), armv7 via the kit gradle task,
host cargo check clean, rustfmt clean, gradle :app/:kit unit tests all pass.
On-device before/after on the Nothing Phone 3 still owed.

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

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

@@ -210,7 +210,9 @@ object NativeBridge {
      * original synchronous pipeline as the per-device escape hatch); [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.
+     * hint otherwise). [presentPriority]/[smoothBuffer] are the timeline presenter's intent
+     * (0 = lowest latency / 1 = smoothness; buffer 0 = automatic, else 1..3 frames) — the Apple
+     * client's `present_priority`/`smooth_buffer` pair. No-op if already started.
      */
     external fun nativeStartVideo(
         handle: Long,
@@ -219,6 +221,8 @@ object NativeBridge {
         lowLatencyMode: Boolean,
         lowLatencyFeature: Boolean,
         isTv: Boolean,
+        presentPriority: Int,
+        smoothBuffer: Int,
     )
 
     /** Stop + join the decode thread without closing the session. No-op on `0`. */
@@ -233,11 +237,11 @@ object NativeBridge {
 
     /**
      * Drain ~1 s of live decode stats for the on-stream HUD, or `null` when no decode thread runs.
-     * Returns 26 doubles (unified stats spec, `design/stats-unification.md`):
+     * Returns 30 doubles (unified stats spec, `design/stats-unification.md`):
      * `[fps, mbps, e2eP50Ms, e2eP95Ms, latValid, skewCorrected, width, height, refreshHz, framesLost,
      * bitDepth, colorPrimaries, colorTransfer, chromaFormatIdc, hostNetP50Ms, decodeP50Ms, hostP50Ms,
      * netP50Ms, lostWindow, skippedWindow, fecWindow, framesWindow, dispValid, displayP50Ms,
-     * e2eDispP50Ms, e2eDispP95Ms]`
+     * e2eDispP50Ms, e2eDispP95Ms, paceP50Ms, latchP50Ms, presentsWindow, presenterActive]`
      * (the flags are 1.0/0.0; indexes 2/3 are the end-to-end capture→decoded headline; 10–13
      * describe the negotiated video feed — bit depth 8/10, CICP primaries/transfer, and the HEVC
      * chroma_format_idc 1=4:2:0 / 3=4:4:4; 14/15 are the stage p50s tiling the headline —