fix(anime): strip disguised HLS segments and report real playback errors

Some hosts prepend a fake image header (a real 1x1 PNG) to every HLS
segment; ffmpeg probes the segment as a picture and mpv drops back to
idle with no window while the browser claims the episode is playing.

- Route bridge-served m3u8 streams through a local strip proxy that
  scans each segment for the first genuine MPEG-TS packet run and drops
  the junk in front of it; playlists get absolute origins rewritten so
  segment requests come back through the proxy. Non-TS bodies pass
  through untouched.
- Only report ok from playEpisode once mpv configures a video output;
  an end-file with reason error surfaces mpv's own message (e.g. "no
  audio or video data played") in the browser status bar instead of
  "Playing". New end-file event plumbed through the mpv IPC client.

src/anime-bridge/playback-outcome.test.ts

@@ -0,0 +1,93 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { watchPlaybackOutcome, type PlaybackEndFileEvent } from './playback-outcome';
+
+type Harness = {
+  emitEndFile: (event: PlaybackEndFileEvent) => void;
+  listenerCount: () => number;
+  setProperty: (name: string, value: unknown) => void;
+  failProperty: (name: string) => void;
+};
+
+function createHarness(overrides?: { timeoutMs?: number; probeIntervalMs?: number }) {
+  const listeners = new Set<(event: PlaybackEndFileEvent) => void>();
+  const properties = new Map<string, unknown>();
+  const failing = new Set<string>();
+
+  const watch = watchPlaybackOutcome({
+    onEndFile: (listener) => {
+      listeners.add(listener);
+      return () => listeners.delete(listener);
+    },
+    readProperty: async (name) => {
+      if (failing.has(name)) throw new Error(`Failed to read MPV property '${name}'`);
+      return properties.get(name);
+    },
+    wait: async () => {},
+    timeoutMs: overrides?.timeoutMs ?? 1000,
+    probeIntervalMs: overrides?.probeIntervalMs ?? 100,
+  });
+
+  const harness: Harness = {
+    emitEndFile: (event) => {
+      for (const listener of listeners) listener(event);
+    },
+    listenerCount: () => listeners.size,
+    setProperty: (name, value) => properties.set(name, value),
+    failProperty: (name) => failing.add(name),
+  };
+  return { watch, harness };
+}
+
+test('resolves ok once mpv configures a video output', async () => {
+  const { watch, harness } = createHarness();
+  harness.setProperty('vo-configured', true);
+  const outcome = await watch.wait();
+  assert.deepEqual(outcome, { ok: true });
+  watch.dispose();
+});
+
+test('resolves failure with the mpv error when the file ends in error', async () => {
+  const { watch, harness } = createHarness();
+  const pending = watch.wait();
+  harness.emitEndFile({ reason: 'error', fileError: 'no audio or video data played' });
+  const outcome = await pending;
+  assert.equal(outcome.ok, false);
+  assert.ok(!outcome.ok && outcome.error.includes('no audio or video data played'));
+  watch.dispose();
+});
+
+test('ignores the end-file fired for the file being replaced', async () => {
+  const { watch, harness } = createHarness();
+  const pending = watch.wait();
+  harness.emitEndFile({ reason: 'stop', fileError: null });
+  harness.setProperty('vo-configured', true);
+  const outcome = await pending;
+  assert.deepEqual(outcome, { ok: true });
+  watch.dispose();
+});
+
+test('times out with a failure when nothing ever starts', async () => {
+  const { watch } = createHarness({ timeoutMs: 300, probeIntervalMs: 100 });
+  const outcome = await watch.wait();
+  assert.equal(outcome.ok, false);
+  assert.ok(!outcome.ok && outcome.error.length > 0);
+  watch.dispose();
+});
+
+test('keeps polling through property read failures', async () => {
+  const { watch, harness } = createHarness();
+  harness.failProperty('vo-configured');
+  const pending = watch.wait();
+  harness.emitEndFile({ reason: 'error', fileError: null });
+  const outcome = await pending;
+  assert.equal(outcome.ok, false);
+  watch.dispose();
+});
+
+test('dispose removes the end-file subscription', () => {
+  const { watch, harness } = createHarness();
+  assert.equal(harness.listenerCount(), 1);
+  watch.dispose();
+  assert.equal(harness.listenerCount(), 0);
+});