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/native/src/decode/sync_loop.rs

@@ -44,6 +44,9 @@ pub(super) fn run_sync(
         ll_feature,
         low_latency_mode,
         is_tv,
+        // The timeline presenter lives in the async loop only; this loop IS the escape hatch.
+        present_priority: _,
+        smooth_buffer: _,
     } = opts;
     boost_thread_priority();
     let mode = client.mode();
@@ -181,7 +184,11 @@ pub(super) fn run_sync(
     // render = true are parked in the tracker; the OnFrameRendered callback pairs them with
     // SurfaceFlinger's render timestamp. `render_cb` is the callback's leaked Arc refcount,
     // reclaimed after the codec is dropped below.
-    let tracker = DisplayTracker::new(stats.clone(), clock_offset.clone());
+    let tracker = DisplayTracker::new(
+        stats.clone(),
+        clock_offset.clone(),
+        std::sync::Arc::new(super::presenter::PresentMeter::new()),
+    );
     let render_cb = install_render_callback(&codec, &tracker);
     // Receipt timestamps keyed by the pts we queue into the codec, so the decoded point (output-
     // buffer dequeue — MediaCodec round-trips presentationTimeUs) can be paired back to its receipt
@@ -598,7 +605,7 @@ fn drain(
             Ok(()) if held_present => {
                 rendered = 1;
                 if let Some((pts_us, decoded_ns)) = meta {
-                    tracker.note_rendered(pts_us, decoded_ns);
+                    tracker.note_rendered(pts_us, decoded_ns, super::latency::now_realtime_ns());
                 }
             }
             Ok(()) => discarded += 1, // held off the screen — awaiting a clean re-anchor