feat: queue UX (Phase M) + media editing (split-chapters, trim)

Phase L (media editing):
- Split by chapters (--split-chapters) as a DownloadOptions toggle
- Trim/cut by time range: parseTrimSections -> --download-sections "*A-B"
  + --force-keyframes-at-cuts (deduped vs SponsorBlock), per-download Trim panel

Phase M (queue & daily-use UX), all 7:
- Pause/resume: main-side killTree + paused flag (silent close), download:pause
  IPC, store pause/resume + paused status, QueueItem controls
- Reorder via "Download next" (prioritize)
- Aggregate progress strip (pure summarizeQueue) + combined speed/ETA
- Drag-and-drop links / .url files onto the download card
- Retry all failed
- Duplicate detection (sameVideo) with "Download anyway" guard
- Per-download scheduling (datetime-local) + save-for-later (saved status,
  15s promotion ticker); session-only (queue not persisted)

New pure modules unit-tested (queueStats); buildArgs trim/split tested.
typecheck + test green (178 passed). Roadmap updated: Phase M COMPLETE.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

test/queueStats.test.ts

@@ -0,0 +1,101 @@
+import { describe, it, expect } from 'vitest'
+import { summarizeQueue, sameVideo } from '../src/renderer/src/store/queueStats'
+import type { DownloadItem } from '../src/renderer/src/store/downloads'
+
+// Minimal item factory — only the fields summarizeQueue reads.
+function item(overrides: Partial<DownloadItem>): DownloadItem {
+  return {
+    id: Math.random().toString(36).slice(2),
+    url: 'https://youtube.com/watch?v=x',
+    title: 'x',
+    kind: 'video',
+    quality: '1080p',
+    status: 'queued',
+    progress: 0,
+    ...overrides
+  }
+}
+
+describe('summarizeQueue', () => {
+  it('counts statuses and flags active', () => {
+    const s = summarizeQueue([
+      item({ status: 'downloading', progress: 0.5 }),
+      item({ status: 'queued' }),
+      item({ status: 'error' }),
+      item({ status: 'completed', progress: 1 }),
+      item({ status: 'canceled' })
+    ])
+    expect(s.downloading).toBe(1)
+    expect(s.queued).toBe(1)
+    expect(s.failed).toBe(1)
+    expect(s.active).toBe(true)
+  })
+
+  it('is inactive and zeroed when nothing is downloading or queued', () => {
+    const s = summarizeQueue([item({ status: 'completed', progress: 1 })])
+    expect(s.active).toBe(false)
+    expect(s.progress).toBe(0)
+    expect(s.speedLabel).toBe('')
+    expect(s.etaLabel).toBe('')
+  })
+
+  it('averages progress over downloading + queued (queued counts as 0%)', () => {
+    // one at 80%, one queued at 0% → 40%
+    const s = summarizeQueue([
+      item({ status: 'downloading', progress: 0.8 }),
+      item({ status: 'queued' })
+    ])
+    expect(s.progress).toBeCloseTo(0.4, 5)
+  })
+
+  it('sums download speeds across MB/s and MiB/s strings', () => {
+    const s = summarizeQueue([
+      item({ status: 'downloading', progress: 0.1, speed: '4.0 MB/s' }),
+      item({ status: 'downloading', progress: 0.1, speed: '2000 KiB/s' })
+    ])
+    // 4.0 MB/s + ~2.0 MB/s ≈ 6.0 MB/s
+    expect(s.speedLabel).toBe('6.0 MB/s')
+  })
+
+  it('reports the longest active ETA as the time left', () => {
+    const s = summarizeQueue([
+      item({ status: 'downloading', progress: 0.5, eta: '0:30' }),
+      item({ status: 'downloading', progress: 0.2, eta: '2:10' })
+    ])
+    expect(s.etaLabel).toBe('2:10')
+  })
+})
+
+describe('sameVideo', () => {
+  it('matches identical URLs', () => {
+    expect(sameVideo('https://x.com/a', 'https://x.com/a')).toBe(true)
+  })
+
+  it('matches YouTube links by video id across watch/youtu.be/extra params', () => {
+    expect(
+      sameVideo(
+        'https://www.youtube.com/watch?v=dQw4w9WgXcQ',
+        'https://youtu.be/dQw4w9WgXcQ'
+      )
+    ).toBe(true)
+    expect(
+      sameVideo(
+        'https://youtube.com/watch?v=dQw4w9WgXcQ&list=PL123',
+        'https://www.youtube.com/watch?v=dQw4w9WgXcQ'
+      )
+    ).toBe(true)
+  })
+
+  it('does not match different videos', () => {
+    expect(
+      sameVideo(
+        'https://youtube.com/watch?v=aaaaaaaaaaa',
+        'https://youtube.com/watch?v=bbbbbbbbbbb'
+      )
+    ).toBe(false)
+  })
+
+  it('normalises www. and trailing slash for non-YouTube URLs', () => {
+    expect(sameVideo('https://www.vimeo.com/123/', 'https://vimeo.com/123')).toBe(true)
+  })
+})