Fix H3/M33/L25/L32: fix probe dependency, correct ipc comment, throttle taskbar, memoize palette

H3: probe.ts now imports fmtBytes from lib/formatters instead of download.ts,
    breaking the circular probe->download dependency direction.
M33: ipc.ts comment corrected to reflect that no batch cap exists; notes the
     known M33 issue for future implementation.
L25: App.tsx taskbar subscriber skips IPC when fraction/mode/badge unchanged,
     eliminating redundant roundtrips on every progress tick.
L32: paletteActions wrapped in useMemo so CommandPalette sees a stable array
     reference; only rebuilds when isDark changes.

typecheck + 242 tests + eslint + prettier green.

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

src/shared/ipc.ts

@@ -659,9 +659,9 @@ export interface BackupImportResult {
 
 // --- Sources & media-manager indexing (Pinchflat-style) ---------------------
 // See ROADMAP-PINCHFLAT.md. A Source (channel/playlist) is indexed once into a
-// persisted list of MediaItem records; the live download queue then pulls from
-// that list a batch at a time, so "download an entire channel" never has to hold
-// the whole collection in the queue at once.
+// persisted list of MediaItem records. When the user downloads pending items,
+// all selected entries are enqueued at once — add a batch cap here if large
+// channel queues (thousands of items) cause performance issues (M33).
 
 /** Whether a Source is a whole channel or a single playlist. */
 export type SourceKind = 'channel' | 'playlist'