feat: self-managing yt-dlp + ffmpeg version display

yt-dlp is now a managed, auto-updating binary rather than a static bundled
one. On launch AeroFetch seeds a writable copy under userData from the
bundled seed, self-heals it if it goes missing, and — throttled to once a
day — self-updates it to the configured channel (default: nightly). This
keeps the binary current so YouTube changes don't silently cause 403s, and
an app reinstall (or portable re-extraction) can no longer roll it back.
Settings shows an auto-update toggle, the live version, last-checked time,
and the channel selector.

Also surface the bundled ffmpeg/ffprobe versions in Settings (display only:
they have no self-update path and, unlike yt-dlp, don't break as sites
change, so there is no auto-update for them).

- binaries: split the read-only bundled seed from the managed userData copy
- ytdlp: ensureManagedYtdlp (seed + self-heal), startup auto-update runner
- ytdlpPolicy: pure once-a-day throttle decision (unit-tested)
- ffmpeg: parse ffmpeg/ffprobe -version for the Settings panel
- settings/ipc/preload/renderer: new settings, IPC channels, types, and UI

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

src/main/ytdlp.ts

@@ -1,13 +1,37 @@
 import { execFile } from 'child_process'
-import { existsSync } from 'fs'
-import { getYtdlpPath } from './binaries'
+import { existsSync, mkdirSync, copyFileSync } from 'fs'
+import { dirname } from 'path'
+import { getYtdlpPath, getBundledYtdlpPath } from './binaries'
+import { getSettings, setSettings } from './settings'
+import { shouldAutoCheckYtdlp } from './ytdlpPolicy'
 import {
   isYtdlpUpdateChannel,
   type YtdlpVersionResult,
   type YtdlpUpdateChannel,
-  type YtdlpUpdateResult
+  type YtdlpUpdateResult,
+  type YtdlpAutoUpdateStatus
 } from '@shared/ipc'
 
+/**
+ * Ensure the writable managed yt-dlp.exe exists, copying the bundled seed in if
+ * it doesn't (first run, or after the user/AV deleted it). Best-effort and
+ * idempotent — when the copy is already present this is just one existsSync, so
+ * it's cheap to call before any spawn/update. Does nothing if the seed itself is
+ * gone (a broken install); callers surface their own missing-binary error then.
+ */
+export function ensureManagedYtdlp(): void {
+  const managed = getYtdlpPath()
+  if (existsSync(managed)) return
+  const seed = getBundledYtdlpPath()
+  if (!existsSync(seed)) return
+  try {
+    mkdirSync(dirname(managed), { recursive: true })
+    copyFileSync(seed, managed)
+  } catch {
+    /* best-effort; a failed seed just leaves the managed copy absent */
+  }
+}
+
 /**
  * Step-1 spike: spawn the bundled yt-dlp and read back `--version`.
  * Proves the main-process → bundled-binary → IPC path end to end.
@@ -51,6 +75,9 @@ export function updateYtdlp(channel: YtdlpUpdateChannel): Promise<YtdlpUpdateRes
     return Promise.resolve({ ok: false, error: 'Unsupported update channel.' })
   }
 
+  // Self-heal: restore the managed copy from the bundled seed before updating, so
+  // a deleted yt-dlp.exe is re-seeded and then updated in one click.
+  ensureManagedYtdlp()
   const ytdlpPath = getYtdlpPath()
 
   if (!existsSync(ytdlpPath)) {
@@ -78,3 +105,45 @@ export function updateYtdlp(channel: YtdlpUpdateChannel): Promise<YtdlpUpdateRes
     )
   })
 }
+
+/**
+ * Startup yt-dlp maintenance: always seed the managed copy, then — if auto-update
+ * is on and the daily throttle has elapsed — self-update it to the configured
+ * channel. Whether it changed is decided by comparing `--version` before/after
+ * (robust against yt-dlp's localized "up to date" wording). Status is pushed to
+ * the renderer so the Settings UI reflects a check it didn't trigger.
+ *
+ * Best-effort: every failure path still records the attempt time (so an
+ * unreachable update server doesn't re-hit the network every launch) and never
+ * throws — a stale binary must never block the app from starting.
+ */
+export async function runStartupYtdlpAutoUpdate(
+  send: (status: YtdlpAutoUpdateStatus) => void
+): Promise<void> {
+  ensureManagedYtdlp()
+  const settings = getSettings()
+  if (!shouldAutoCheckYtdlp(settings.autoUpdateYtdlp, settings.ytdlpLastUpdateCheck, Date.now())) {
+    return
+  }
+
+  const channel = settings.ytdlpChannel
+  send({ phase: 'checking', channel })
+
+  const before = await getYtdlpVersion()
+  const result = await updateYtdlp(channel)
+  setSettings({ ytdlpLastUpdateCheck: Date.now() })
+
+  if (!result.ok) {
+    send({ phase: 'error', channel, error: result.error, checkedAt: Date.now() })
+    return
+  }
+
+  const after = await getYtdlpVersion()
+  const changed = before.ok && after.ok && before.version !== after.version
+  send({
+    phase: changed ? 'updated' : 'current',
+    channel,
+    version: after.ok ? after.version : undefined,
+    checkedAt: Date.now()
+  })
+}