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/core/services/youtube/metadata-probe.test.ts

@@ -0,0 +1,89 @@
+import assert from 'node:assert/strict';
+import fs from 'node:fs';
+import os from 'node:os';
+import path from 'node:path';
+import test from 'node:test';
+import { probeYoutubeVideoMetadata } from './metadata-probe';
+
+async function withTempDir<T>(fn: (dir: string) => Promise<T>): Promise<T> {
+  const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'subminer-youtube-metadata-probe-'));
+  try {
+    return await fn(dir);
+  } finally {
+    fs.rmSync(dir, { recursive: true, force: true });
+  }
+}
+
+function makeFakeYtDlpScript(dir: string, payload: string): void {
+  const scriptPath = path.join(dir, 'yt-dlp');
+  const script = `#!/usr/bin/env node
+process.stdout.write(${JSON.stringify(payload)});
+`;
+  fs.writeFileSync(scriptPath, script, 'utf8');
+  if (process.platform !== 'win32') {
+    fs.chmodSync(scriptPath, 0o755);
+  }
+  fs.writeFileSync(scriptPath + '.cmd', `@echo off\r\nnode "${scriptPath}"\r\n`, 'utf8');
+}
+
+function makeHangingFakeYtDlpScript(dir: string): void {
+  const scriptPath = path.join(dir, 'yt-dlp');
+  const script = `#!/usr/bin/env node
+setInterval(() => {}, 1000);
+`;
+  fs.writeFileSync(scriptPath, script, 'utf8');
+  if (process.platform !== 'win32') {
+    fs.chmodSync(scriptPath, 0o755);
+  }
+  fs.writeFileSync(scriptPath + '.cmd', `@echo off\r\nnode "${scriptPath}"\r\n`, 'utf8');
+}
+
+async function withFakeYtDlp<T>(payload: string, fn: () => Promise<T>): Promise<T> {
+  return await withTempDir(async (root) => {
+    const binDir = path.join(root, 'bin');
+    fs.mkdirSync(binDir, { recursive: true });
+    makeFakeYtDlpScript(binDir, payload);
+    const originalPath = process.env.PATH ?? '';
+    process.env.PATH = `${binDir}${path.delimiter}${originalPath}`;
+    try {
+      return await fn();
+    } finally {
+      process.env.PATH = originalPath;
+    }
+  });
+}
+
+async function withHangingFakeYtDlp<T>(fn: () => Promise<T>): Promise<T> {
+  return await withTempDir(async (root) => {
+    const binDir = path.join(root, 'bin');
+    fs.mkdirSync(binDir, { recursive: true });
+    makeHangingFakeYtDlpScript(binDir);
+    const originalPath = process.env.PATH ?? '';
+    process.env.PATH = `${binDir}${path.delimiter}${originalPath}`;
+    try {
+      return await fn();
+    } finally {
+      process.env.PATH = originalPath;
+    }
+  });
+}
+
+test('probeYoutubeVideoMetadata returns null on malformed yt-dlp JSON', async () => {
+  await withFakeYtDlp('not-json', async () => {
+    const result = await probeYoutubeVideoMetadata('https://www.youtube.com/watch?v=abc123');
+    assert.equal(result, null);
+  });
+});
+
+test(
+  'probeYoutubeVideoMetadata times out when yt-dlp hangs',
+  { timeout: 20_000 },
+  async () => {
+    await withHangingFakeYtDlp(async () => {
+      await assert.rejects(
+        probeYoutubeVideoMetadata('https://www.youtube.com/watch?v=abc123'),
+        /timed out after 15000ms/,
+      );
+    });
+  },
+);