feat(android): tiered stats HUD + windowed lost/skipped/FEC counters

Stats overlay verbosity tiers (Off/Compact/Normal/Detailed, 3-finger tap
cycles live, old Boolean pref migrated) and the unified-spec line-4
reliability counters: lost/FEC windowed from the connector's cumulative
totals, skipped from the client's own newest-wins drops. Adds the
fec_recovered_shards accessor to NativeClient, mirrored from the
data-plane pump like frames_dropped.

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

clients/android/native/src/session/planes.rs

@@ -144,16 +144,20 @@ pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeStopVideo(
 }
 
 /// `NativeBridge.nativeVideoStats(handle): DoubleArray?` — drain ~1 s of decode stats for the HUD
-/// (unified stats spec, `design/stats-unification.md`). Returns 18 doubles
+/// (unified stats spec, `design/stats-unification.md`). Returns 22 doubles
 /// `[fps, mbps, e2eP50Ms, e2eP95Ms, latValid, skewCorrected, width, height, refreshHz, framesLost,
 /// bitDepth, colorPrimaries, colorTransfer, chromaFormatIdc, hostNetP50Ms, decodeP50Ms, hostP50Ms,
-/// netP50Ms]`
-/// (the two flags are 1.0/0.0; indexes 0–15 match the previous 16-double layout — 0–13 the original
+/// netP50Ms, lostWindow, skippedWindow, fecWindow, framesWindow]`
+/// (the two flags are 1.0/0.0; indexes 0–17 match the previous 18-double layout — 0–13 the original
 /// 14-double one with the latency pair re-based to the end-to-end capture→decoded headline, 14/15
 /// the stage p50s tiling it: `host+network` = capture→received, `decode` = received→decoded; 16/17
 /// are the Phase-2 split of the `host+network` term from the per-AU 0xCF host timings — `host` =
 /// the host's capture→sent, `network` = the remainder — both 0.0 when no timing matched this
-/// window, i.e. an old host), or `null` when no decode thread is running. Poll ~1 Hz from the UI; each call
+/// window, i.e. an old host; 18–21 are the spec's per-window line-4 counters — `lost` =
+/// unrecoverable drops this window, `skipped` = client newest-wins/pacing drops, `fec` = shards
+/// recovered, `frames` = AUs received, so the HUD can compute `lost/(frames+lost)` — index 9 stays
+/// the cumulative session total for older readers), or `null` when no decode thread is running.
+/// Poll ~1 Hz from the UI; each call
 /// resets the measurement window. Not android-gated — pure `jni` + connector reads, so it links on
 /// the host build too (Kotlin only ever calls it on device).
 #[no_mangle]
@@ -171,10 +175,12 @@ pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeVideoStats(
         if h.video.lock().unwrap().is_none() {
             return std::ptr::null_mut(); // not streaming → no stats
         }
-        let snap = h.stats.drain();
+        let snap = h
+            .stats
+            .drain(h.client.frames_dropped(), h.client.fec_recovered_shards());
         let mode = h.client.mode();
         let color = h.client.color;
-        let buf: [f64; 18] = [
+        let buf: [f64; 22] = [
             snap.fps,
             snap.mbps,
             snap.e2e_p50_ms,
@@ -200,6 +206,13 @@ pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeVideoStats(
             // when no timing matched this window (old host) — the HUD keeps the combined term.
             snap.host_p50_ms,
             snap.net_p50_ms,
+            // Spec line-4 counters, per-window: lost (unrecoverable drops), skipped (client
+            // newest-wins/pacing drops), FEC shards recovered, and the received-AU count so the
+            // HUD computes the loss percentage `lost/(frames+lost)` exactly.
+            snap.lost as f64,
+            snap.skipped as f64,
+            snap.fec as f64,
+            snap.frames as f64,
         ];
         let arr = match env.new_double_array(buf.len() as jsize) {
             Ok(a) => a,
@@ -228,7 +241,13 @@ pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeSetVideoSta
         if handle != 0 {
             // SAFETY: live handle per the nativeConnect/nativeClose contract.
             let h = unsafe { &*(handle as *const SessionHandle) };
-            h.stats.set_enabled(enabled != 0);
+            // The current cumulative counters seed the window baselines, so the first snapshot's
+            // `lost`/`FEC` cover only time the HUD was actually up.
+            h.stats.set_enabled(
+                enabled != 0,
+                h.client.frames_dropped(),
+                h.client.fec_recovered_shards(),
+            );
         }
     })
 }