feat(playback): report Embedded MPV file chapters on the timeline

Observe mpv `chapter-list` in the macOS and Windows addons and the
frame-copy helper, carry it as `EmbeddedMpvSession.chapters`, and map it
to `PlayerTimelineSegment[]` for `app-player-controls` when the host
passes no catch-up segments. A closing-credits chapter now times the
Up next card.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/electron-backend-e2e/src/embedded-mpv-chapters.e2e.ts

@@ -0,0 +1,129 @@
+import { readFileSync, writeFileSync } from 'fs';
+import { join } from 'path';
+import {
+    channelItemByTitle,
+    closeElectronApp,
+    expect,
+    goToDashboard,
+    importM3uPlaylistFromNativeDialog,
+    launchElectronApp,
+    openSettings,
+    openSettingsSection,
+    saveSettings,
+    test,
+    workspaceRoot,
+} from './electron-test-fixtures';
+import {
+    createLocalMediaServer,
+    installEmbeddedMpvSessionCapture,
+} from './embedded-mpv-frame-copy-packaged-fixtures';
+
+/**
+ * mpv's `chapter-list` must reach the shared controls: the chaptered fixture
+ * (Intro 0 s, Episode 5 s, Credits 24 s of 30 s) is drawn as three titled
+ * timeline segments. Frame-copy is the Embedded MPV engine that mounts
+ * `app-player-controls`; the test skips where that runtime is unavailable.
+ */
+test('@playback @electron @embedded-mpv frame-copy draws file chapters on the timeline', async ({
+    dataDir,
+}) => {
+    const media = await createLocalMediaServer({
+        body: readFileSync(
+            join(
+                workspaceRoot,
+                'apps/web-e2e/src/fixtures/playback/episode-chapters.webm'
+            )
+        ),
+        resourcePath: '/episode-chapters.webm',
+        contentType: 'video/webm',
+    });
+    const app = await launchElectronApp(dataDir, {
+        env: {
+            IPTVNATOR_ENABLE_EMBEDDED_MPV_EXPERIMENT: '1',
+            IPTVNATOR_ENABLE_EMBEDDED_MPV_FRAME_COPY: '1',
+            IPTVNATOR_EMBEDDED_MPV_ALLOW_HOMEBREW: '1',
+        },
+    });
+    try {
+        const support = await app.mainWindow.evaluate(() =>
+            window.electron.getEmbeddedMpvSupport()
+        );
+        test.skip(
+            !support.supported || support.engine !== 'frame-copy',
+            `Frame-copy runtime unavailable: ${JSON.stringify(support)}`
+        );
+        await openSettings(app.mainWindow);
+        await openSettingsSection(app.mainWindow, 'playback');
+        await app.mainWindow.getByTestId('select-video-player').click();
+        await app.mainWindow.getByTestId('embedded-mpv').click();
+        await saveSettings(app.mainWindow);
+        await goToDashboard(app.mainWindow);
+
+        const playlist = join(dataDir, 'chapters.m3u');
+        writeFileSync(
+            playlist,
+            `#EXTM3U\n#EXTINF:-1,Chaptered fixture\n${media.url}\n`
+        );
+        await installEmbeddedMpvSessionCapture(app);
+        await importM3uPlaylistFromNativeDialog(app, playlist);
+        await channelItemByTitle(app.mainWindow, 'Chaptered fixture')
+            .first()
+            .click();
+
+        // The local frame-copy runtime can fail its first frame-view
+        // initialization; one user Retry recovers it (see player-theme).
+        await expect
+            .poll(() =>
+                app.mainWindow.evaluate(
+                    () =>
+                        (window.__packagedEmbeddedMpvSessions?.at(-1)?.chapters
+                            ?.length ?? 0) > 0 ||
+                        !!document.querySelector('.embedded-mpv-player__stalled')
+                ),
+                { timeout: 20000 }
+            )
+            .toBe(true);
+        const stalled = app.mainWindow.locator('.embedded-mpv-player__stalled');
+        if (await stalled.isVisible()) {
+            await stalled.getByRole('button', { name: 'Retry' }).click();
+        }
+
+        await expect
+            .poll(
+                () =>
+                    app.mainWindow.evaluate(
+                        () =>
+                            window.__packagedEmbeddedMpvSessions?.at(-1)
+                                ?.chapters ?? []
+                    ),
+                { timeout: 20000 }
+            )
+            .toEqual([
+                { timeSeconds: 0, title: 'Intro' },
+                { timeSeconds: 5, title: 'Episode' },
+                { timeSeconds: 24, title: 'Credits' },
+            ]);
+
+        const segments = app.mainWindow.locator(
+            'app-player-controls .player-controls__timeline-segment'
+        );
+        await expect(segments).toHaveCount(3);
+        await expect
+            .poll(() =>
+                segments.evaluateAll((elements) =>
+                    elements.map((element) => ({
+                        title: element.getAttribute('data-segment-title'),
+                        left: Math.round(parseFloat(element.style.left)),
+                    }))
+                )
+            )
+            .toEqual([
+                { title: 'Intro', left: 0 },
+                { title: 'Episode', left: 17 },
+                { title: 'Credits', left: 80 },
+            ]);
+    } finally {
+        await closeElectronApp(app);
+        await media.close();
+    }
+});

apps/electron-backend-e2e/src/embedded-mpv-frame-copy-packaged.e2e.ts

@@ -360,12 +360,23 @@ test.describe('Packaged Linux embedded MPV frame-copy runtime', () => {
                 resourcePath: '/stream-stats-switch.webm',
                 contentType: 'video/webm',
             });
+            const chapteredMedia = await createLocalMediaServer({
+                body: readFileSync(
+                    join(
+                        __dirname,
+                        '../../web-e2e/src/fixtures/playback/episode-chapters.webm'
+                    )
+                ),
+                resourcePath: '/chapters.webm',
+                contentType: 'video/webm',
+            });
             media = {
                 url: mediaServer.url,
                 close: async () => {
                     await Promise.all([
                         mediaServer.close(),
                         alternateMedia.close(),
+                        chapteredMedia.close(),
                     ]);
                 },
             };
@@ -415,6 +426,33 @@ test.describe('Packaged Linux embedded MPV frame-copy runtime', () => {
                     });
             }
 
+            // mpv's `chapter-list` reaches the renderer session (it draws the
+            // timeline segments and times the Up next card), and the next
+            // file starts without the previous file's chapters.
+            await launchedFrameCopyApp.mainWindow.evaluate(
+                async ({ sessionId, streamUrl }) => {
+                    await window.electron.loadEmbeddedMpvPlayback(sessionId, {
+                        streamUrl,
+                        title: 'Chaptered episode',
+                        isLive: false,
+                    });
+                },
+                { sessionId: created.id, streamUrl: chapteredMedia.url }
+            );
+            await expect
+                .poll(
+                    () => getLatestSession(launchedFrameCopyApp, created.id),
+                    { timeout: 15000 }
+                )
+                .toMatchObject({
+                    streamUrl: chapteredMedia.url,
+                    chapters: [
+                        { timeSeconds: 0, title: 'Intro' },
+                        { timeSeconds: 5, title: 'Episode' },
+                        { timeSeconds: 24, title: 'Credits' },
+                    ],
+                });
+
             // Audio-only replacements must not retain the previous video size.
             await launchedFrameCopyApp.mainWindow.evaluate(
                 async ({ sessionId, streamUrl }) => {
@@ -433,6 +471,7 @@ test.describe('Packaged Linux embedded MPV frame-copy runtime', () => {
                 )
                 .toMatchObject({
                     streamUrl: audioMedia.url,
+                    chapters: [],
                     videoWidth: 0,
                     videoHeight: 0,
                     stats: {