feat(audit): Batch 13 — copy polish + misc-L cleanup

Contained fixes:
- L158: drag-highlight flicker. useDownloadBar tracks a dragDepth counter —
  onDragEnter increments, onDragLeave decrements, the highlight clears only when
  depth returns to 0 (the drag truly left the card). onDragOver just
  preventDefaults; onDrop resets. No more blink when crossing child elements.
- L92: preload method names aligned with main — markSourceItemDownloaded →
  setMediaItemDownloaded, syncSources → syncWatchedSources (callers + mock
  updated; compiler-enforced via the derived Api type).
- L149: the three-sentence "Keep running in the tray" hint is now one line.
- L171: one MOCK_CURRENT_VERSION backs both the preview mock's getAppVersion and
  checkForAppUpdate.currentVersion, so they agree.
- L5 (representative): the About card's repeated monospace inline styles → shared
  mono/monoBlock/monoPre classes; convention set (makeStyles for static, inline
  style only for data-driven values).

Resolved by verification/convention (CODE-AUDIT.md): L21 (moot after the H1
SettingsView decomposition), L31 (dual theme switcher is width-driven), L130
(lowercase fragments vs shown-raw sentences), L152 (search sizes are role-
appropriate), UI22 (brand/entity/section icon-emphasis set now defined).

Deferred with rationale: L51/L64 (features), L93 (CC13 view-model pass), L104
(moved to Batch 14 perf), L109/UI21 (visual), L161/UI23 (layout/live-verify).

Verified: typecheck (node+web) + 279 tests + eslint + production build green;
touched files prettier-clean.

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

src/preload/index.ts

@@ -199,16 +199,18 @@ const api = {
   listSourceItems: (sourceId: string): Promise<MediaItem[]> =>
     ipcRenderer.invoke(IpcChannels.sourceItems, sourceId),
 
-  /** Persist that a media item has finished downloading (drives incremental sync). */
-  markSourceItemDownloaded: (id: string, filePath?: string): Promise<MediaItem[]> =>
+  /** Persist that a media item has finished downloading (drives incremental sync).
+   *  Named to match the main handler `setMediaItemDownloaded` (L92). */
+  setMediaItemDownloaded: (id: string, filePath?: string): Promise<MediaItem[]> =>
     ipcRenderer.invoke(IpcChannels.sourceItemDownloaded, id, filePath),
 
   /** Toggle whether a source is watched for new uploads. */
   setSourceWatched: (id: string, watched: boolean): Promise<Source[]> =>
     ipcRenderer.invoke(IpcChannels.sourceSetWatched, id, watched),
 
-  /** Re-index all watched sources; resolves with the videos found new. */
-  syncSources: (): Promise<SyncResult> => ipcRenderer.invoke(IpcChannels.sourcesSync),
+  /** Re-index all watched sources; resolves with the videos found new. Named to
+   *  match the main function `syncWatchedSources` (L92). */
+  syncWatchedSources: (): Promise<SyncResult> => ipcRenderer.invoke(IpcChannels.sourcesSync),
 
   /** Read / write the Windows daily-sync scheduled task. */
   getScheduledSync: (): Promise<ScheduledSyncStatus> =>