fix(workspace): keep the overlay delay while another playlist refreshes

Refresh preparation skipped the cached-load delay for any playlist, so
opening a cached portal while another playlist prepared a refresh still
flashed the overlay. Only preparation of the shown playlist (any on the
dashboard) now shows it at once.

Also words the J2 layout-shift history from #1895 in the past tense: the
cached-load overlay no longer mounts on a J2 click.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/architecture/performance-journeys.md

@@ -1322,8 +1322,8 @@ largest distance in it, the content pane's 323 px, which is why Back added
 buttons appearing when the categories arrive. The skeletons of the category
 list and the grid are replaced by content without any shift. Nothing was
 hidden behind the startup overlay: the "Syncing playlist" overlay of the
-cached catalog load flashes for about two frames after the shift and covers
-no further one.
+cached catalog load flashed for about two frames after the shift and covered
+no further one. It no longer mounts on a J2 click (see the J2 section).
 
 The content frame and the header controls now slide into place instead of
 jumping ([Layout slides](./workspace-shell.md#layout-slides)): the new layout

docs/architecture/workspace-shell.md

@@ -195,9 +195,10 @@ services:
 5. `WorkspaceShellCommandPaletteService` owns command-palette dialog lifecycle
    and recent-command recording.
 6. `WorkspaceShellXtreamImportService` owns Xtream import/refresh overlay
-   state and labels. Remote import phases and refresh preparation show the
-   overlay at once. A session that has only read the saved catalog
-   (`loading-cached`, `isImporting` still false) shows it only after
+   state and labels. Remote import phases and refresh preparation of the
+   shown playlist (of any playlist on the dashboard) show the overlay at
+   once. A session that has only read the saved catalog (`loading-cached`,
+   `isImporting` still false) shows it only after
    `XTREAM_LOCAL_LOAD_OVERLAY_DELAY_MS` (300 ms), so a warm open goes from
    the skeleton to the page without flashing the overlay, while a slow or
    stuck cache read still blocks and stays cancellable.