feat: add app-owned YouTube subtitle flow with absPlayer-style parsing (#31)

* fix: harden preload argv parsing for popup windows

* fix: align youtube playback with shared overlay startup

* fix: unwrap mpv youtube streams for anki media mining

* docs: update docs for youtube subtitle and mining flow

* refactor: unify cli and runtime wiring for startup and youtube flow

* feat: update subtitle sidebar overlay behavior

* chore: add shared log-file source for diagnostics

* fix(ci): add changelog fragment for immersion changes

* fix: address CodeRabbit review feedback

* fix: persist canonical title from youtube metadata

* style: format stats library tab

* fix: address latest review feedback

* style: format stats library files

* test: stub launcher youtube deps in CI

* test: isolate launcher youtube flow deps

* test: stub launcher youtube deps in failing case

* test: force x11 backend in launcher ci harness

* test: address latest review feedback

* fix(launcher): preserve user YouTube ytdl raw options

* docs(backlog): update task tracking notes

* fix(immersion): special-case youtube media paths in runtime and tracking

* feat(stats): improve YouTube media metadata and picker key handling

* fix(ci): format stats media library hook

* fix: address latest CodeRabbit review items

* docs: update youtube release notes and docs

* feat: auto-load youtube subtitles before manual picker

* fix: restore app-owned youtube subtitle flow

* docs: update youtube playback docs and config copy

* refactor: remove legacy youtube launcher mode plumbing

* fix: refine youtube subtitle startup binding

* docs: clarify youtube subtitle startup behavior

* fix: address PR #31 latest review follow-ups

* fix: address PR #31 follow-up review comments

* test: harden youtube picker test harness

* udpate backlog

* fix: add timeout to youtube metadata probe

* docs: refresh youtube and stats docs

* update backlog

* update backlog

* chore: release v0.9.0

src/main/runtime/youtube-playback.ts

@@ -0,0 +1,39 @@
+function trimToNull(value: string | null | undefined): string | null {
+  if (typeof value !== 'string') {
+    return null;
+  }
+  const trimmed = value.trim();
+  return trimmed.length > 0 ? trimmed : null;
+}
+
+function matchesYoutubeHost(hostname: string, expectedHost: string): boolean {
+  return hostname === expectedHost || hostname.endsWith(`.${expectedHost}`);
+}
+
+export function isYoutubeMediaPath(mediaPath: string | null | undefined): boolean {
+  const normalized = trimToNull(mediaPath);
+  if (!normalized) {
+    return false;
+  }
+
+  let parsed: URL;
+  try {
+    parsed = new URL(normalized);
+  } catch {
+    return false;
+  }
+
+  const host = parsed.hostname.toLowerCase();
+  return (
+    matchesYoutubeHost(host, 'youtu.be') ||
+    matchesYoutubeHost(host, 'youtube.com') ||
+    matchesYoutubeHost(host, 'youtube-nocookie.com')
+  );
+}
+
+export function isYoutubePlaybackActive(
+  currentMediaPath: string | null | undefined,
+  currentVideoPath: string | null | undefined,
+): boolean {
+  return isYoutubeMediaPath(currentMediaPath) || isYoutubeMediaPath(currentVideoPath);
+}