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>

src/main/buildArgs.ts

@@ -161,6 +161,30 @@ export function selectExtraArgs(params: {
   return []
 }
 
+/**
+ * Parse a raw trim string (one or more time ranges, comma- or newline-separated)
+ * into yt-dlp `--download-sections` specs. Each range is normalised to the
+ * `*START-END` time-range form yt-dlp expects (the leading `*` distinguishes a
+ * timestamp range from a chapter-title regex). Tokens that don't look like a
+ * numeric time range are dropped, so malformed input can't reach yt-dlp's argv.
+ *
+ * Accepts H:MM:SS / M:SS / SS with optional fractional seconds, e.g. '1:30-2:00',
+ * '90-120', '0:00:10.5-0:00:20'. A token may already carry the leading `*`.
+ */
+export function parseTrimSections(raw: string | undefined): string[] {
+  if (!raw) return []
+  const TIME = String.raw`\d+(?::\d{1,2})*(?:\.\d+)?`
+  const RANGE = new RegExp(`^${TIME}-${TIME}$`)
+  const out: string[] = []
+  for (const piece of raw.split(/[,\n]/)) {
+    let t = piece.trim()
+    if (!t) continue
+    if (t.startsWith('*')) t = t.slice(1).trim()
+    if (RANGE.test(t)) out.push(`*${t}`)
+  }
+  return out
+}
+
 // Wrap a single argv token for human-readable display only (Phase C command
 // preview) — never used to build the real argv that gets spawned.
 function quoteForDisplay(arg: string): string {
@@ -250,17 +274,30 @@ function postProcessArgs(opts: StartDownloadOptions, o: DownloadOptions): string
   }
 
   // SponsorBlock.
+  let forcedKeyframes = false
   if (o.sponsorBlock && o.sponsorBlockCategories.length > 0) {
     const cats = o.sponsorBlockCategories.join(',')
     if (o.sponsorBlockMode === 'remove') {
       // Force keyframes at the cut points so segment boundaries are frame-accurate.
       args.push('--sponsorblock-remove', cats, '--force-keyframes-at-cuts')
+      forcedKeyframes = true
     } else {
       args.push('--sponsorblock-mark', cats)
     }
   }
 
+  // Trim — download only the given time ranges (works for video + audio). Force
+  // keyframes at the cut points for frame-accurate boundaries, unless
+  // SponsorBlock-remove already requested it (the flag is idempotent, but we
+  // avoid emitting it twice).
+  const sections = parseTrimSections(opts.trim)
+  for (const sec of sections) args.push('--download-sections', sec)
+  if (sections.length > 0 && !forcedKeyframes) args.push('--force-keyframes-at-cuts')
+
   if (o.embedChapters) args.push('--embed-chapters')
+  // Split into one file per chapter. yt-dlp also keeps the full file; the
+  // per-chapter files use yt-dlp's default `chapter:` output template.
+  if (o.splitChapters) args.push('--split-chapters')
   if (o.embedMetadata) args.push('--embed-metadata')
 
   // Media-server sidecar files (Phase K) — written next to the output file so

src/main/download.ts

@@ -38,6 +38,7 @@ import {
 interface ActiveDownload {
   child: ChildProcess
   canceled: boolean
+  paused: boolean
 }
 
 const active = new Map<string, ActiveDownload>()
@@ -295,7 +296,7 @@ export function startDownload(
     return { ok: false, error: (e as Error).message }
   }
 
-  const rec: ActiveDownload = { child, canceled: false }
+  const rec: ActiveDownload = { child, canceled: false, paused: false }
   active.set(opts.id, rec)
 
   // Title/channel/duration are kept locally so the completion notification and
@@ -344,7 +345,8 @@ export function startDownload(
     if (settled) return
     settled = true
     active.delete(opts.id)
-    if (!rec.canceled) {
+    // A paused download was killed on purpose — stay silent, like a cancel.
+    if (!rec.canceled && !rec.paused) {
       send(wc, { type: 'error', id: opts.id, error: err.message })
       logFailure(opts, resolvedTitle, err.message)
       notify(wc, resolvedTitle ?? 'Download failed', err.message)
@@ -355,7 +357,9 @@ export function startDownload(
     if (settled) return
     settled = true
     active.delete(opts.id)
-    if (rec.canceled) return // renderer already showed 'canceled' optimistically
+    // Canceled: renderer already showed 'canceled'. Paused: renderer showed
+    // 'paused' and keeps the .part for a later resume. Either way, no event.
+    if (rec.canceled || rec.paused) return
     if (code === 0) {
       send(wc, { type: 'done', id: opts.id, filePath })
       notify(wc, resolvedTitle ?? 'Download complete', 'Finished downloading.')
@@ -370,15 +374,12 @@ export function startDownload(
   return { ok: true }
 }
 
-export function cancelDownload(id: string): void {
-  const rec = active.get(id)
-  if (!rec) return
-  rec.canceled = true
+// Kill the whole process tree (/T) so the spawned ffmpeg child dies too. Resolve
+// taskkill from System32 by absolute path, never the bare name, so a planted
+// taskkill.exe on PATH / in the CWD can't run in its place. (audit F3)
+function killTree(rec: ActiveDownload): void {
   const pid = rec.child.pid
   if (pid != null) {
-    // Kill the whole tree (/T) so the spawned ffmpeg child dies too. Resolve
-    // taskkill from System32 by absolute path, never the bare name, so a planted
-    // taskkill.exe on PATH / in the CWD can't run in its place. (audit F3)
     execFile(
       getSystem32Path('taskkill.exe'),
       ['/pid', String(pid), '/T', '/F'],
@@ -389,3 +390,24 @@ export function cancelDownload(id: string): void {
     rec.child.kill()
   }
 }
+
+export function cancelDownload(id: string): void {
+  const rec = active.get(id)
+  if (!rec) return
+  rec.canceled = true
+  killTree(rec)
+}
+
+/**
+ * Pause a running download: kill the process tree but flag it `paused` (not
+ * `canceled`) so the close handler stays silent — no error event, no error log,
+ * no notification. yt-dlp leaves the partial `.part` file in place, so resuming
+ * is just a fresh startDownload with the same options: yt-dlp's default
+ * `--continue` picks the partial file back up.
+ */
+export function pauseDownload(id: string): void {
+  const rec = active.get(id)
+  if (!rec) return
+  rec.paused = true
+  killTree(rec)
+}

src/main/index.ts

@@ -14,7 +14,7 @@ import { getYtdlpVersion, updateYtdlp, runStartupYtdlpAutoUpdate } from './ytdlp
 import { getFfmpegVersions } from './ffmpeg'
 import { checkForAppUpdate, downloadAppUpdate, runAppUpdate } from './updater'
 import { probeMedia } from './probe'
-import { startDownload, cancelDownload, previewCommand } from './download'
+import { startDownload, cancelDownload, pauseDownload, previewCommand } from './download'
 import { getSettings, setSettings, ensureMediaDirs } from './settings'
 import { listHistory, addHistory, removeHistory, removeManyHistory, clearHistory } from './history'
 import { listTemplates, saveTemplate, removeTemplate } from './templates'
@@ -211,6 +211,7 @@ function registerIpcHandlers(): void {
     return result
   })
   ipcMain.handle(IpcChannels.downloadCancel, (_e, id: string) => cancelDownload(id))
+  ipcMain.handle(IpcChannels.downloadPause, (_e, id: string) => pauseDownload(id))
 
   ipcMain.handle(IpcChannels.defaultFolder, () => app.getPath('downloads'))
 

src/main/settings.ts

@@ -111,6 +111,7 @@ function sanitizeOptions(input: unknown): DownloadOptions {
     sponsorBlockMode: o.sponsorBlockMode === 'mark' ? 'mark' : 'remove',
     sponsorBlockCategories: cats,
     embedChapters: bool(o.embedChapters, d.embedChapters),
+    splitChapters: bool(o.splitChapters, d.splitChapters),
     embedMetadata: bool(o.embedMetadata, d.embedMetadata),
     embedThumbnail: bool(o.embedThumbnail, d.embedThumbnail),
     cropThumbnail: bool(o.cropThumbnail, d.cropThumbnail),