fix(android): keep the display awake while video plays

Android counts its display timeout from the last user input, and watching
something is exactly the case where there is none — so the screen dimmed and
slept mid-playback unless the user kept tapping it.

Nothing held it. FLAG_KEEP_SCREEN_ON appeared nowhere in the app, and neither
renderer supplies a hold for free: ExoPlayer's setWakeMode is a CPU/wifi wake
lock that says nothing about the display, and it draws into the TextureView we
own (DR-192) rather than media3's PlayerView, which is the widget that would
otherwise set keepScreenOn itself; the webview <video> path is no better,
because the display wake lock Chrome takes for video lives in the browser layer
and not in an embedded WebView.

ScreenWakeManager toggles FLAG_KEEP_SCREEN_ON on the Activity window — window
scoped, so it stops applying the moment the app is not visible and cannot
outlive a crash the way an acquired PowerManager.WakeLock can, and it needs no
permission. The two rendering paths are independent holders OR-ed in the pure
ScreenWakeState: the native path follows onIsPlayingChanged plus surface
teardown, so the hold tracks what ExoPlayer reports rather than what the UI
intends, and the webview path reuses the setHtml5VideoState report the frontend
already sends for PiP. Audio is deliberately not a holder — screen-off music is
the point of that path.

Also the repo's first Kotlin JVM unit tests: ScreenWakeState is framework-free,
so the decision is testable off-device with

    ./gradlew :app:testUniversalDebugUnitTest

(note the variant — plain testDebugUnitTest is ambiguous here). sync-android
-sources.sh mirrors src/test into the gen tree alongside the main sources.

TRACES: UR-003, UR-004 | DR-202 | UT-199

scripts/extract-traces.test.ts

@@ -270,9 +270,10 @@ describe("live requirements.md", () => {
     // scope/CSP), DR-199 (webview mixed-content) and DR-200 (the
     // POST_NOTIFICATIONS media-session exemption; renumbered from 198 on
     // merge, where it collided). Each branch bumped for its own — merged,
-    // they sum. Resolve this by summing, never by taking one side.
-    expect(defined.DR).toBe(192);
+    // they sum. Resolve this by summing, never by taking one side. 193 adds
+    // DR-202 (video keeps the display awake).
+    expect(defined.DR).toBe(193);
     expect(defined.JA).toBe(36);
-    expect(defined.total).toBe(335);
+    expect(defined.total).toBe(336);
   });
 });

scripts/sync-android-sources.sh

@@ -23,6 +23,19 @@ rm -rf "$TARGET_DIR/player" "$TARGET_DIR/security"
 cp -r "$SOURCE_DIR/player" "$TARGET_DIR/"
 cp -r "$SOURCE_DIR/security" "$TARGET_DIR/"
 
+# JVM unit tests (src/test). Plain JUnit over the pure decision helpers — no
+# Android framework classes — run with `./gradlew :app:testDebugUnitTest` from
+# gen/android. Mirrored here so the canonical tree stays the only place tests
+# are edited.
+TEST_SOURCE_DIR="$PROJECT_ROOT/src-tauri/android/src/test/java/com/dtourolle/jellytau"
+TEST_TARGET_DIR="$PROJECT_ROOT/src-tauri/gen/android/app/src/test/java/com/dtourolle/jellytau"
+if [ -d "$TEST_SOURCE_DIR" ]; then
+    rm -rf "$TEST_TARGET_DIR"
+    mkdir -p "$TEST_TARGET_DIR"
+    cp -r "$TEST_SOURCE_DIR"/. "$TEST_TARGET_DIR/"
+    echo "  Copied unit tests: src/test"
+fi
+
 # Copy individual Kotlin files (like VideoOverlayManager.kt)
 for kt_file in "$SOURCE_DIR"/*.kt; do
     if [ -f "$kt_file" ]; then