feat(overlay): add loading OSD spinner and queue notifications until ren

- Show mpv OSD spinner from start-file until subminer-overlay-loading-ready; force-shown for visible-overlay startup regardless of osd_messages setting
- Gate non-macOS overlay visibility on content-ready so first subtitle line is immediately hoverable and clickable
- Queue startup notifications in main process until overlay window finishes loading; upsert progress cards by id to avoid cold-start floods
- Defer background warmups until after overlay runtime init so queued notifications can deliver promptly
- Preserve character dictionary checking/building/importing/ready phases as distinct history entries; route building and importing to system notifications when notificationType is both

changes/overlay-notifications.md

@@ -5,9 +5,10 @@ breaking: true
 - Added overlay notifications with a Catppuccin Macchiato stack, a 3-second transient timeout, and persistent long-running job notifications for character dictionary sync.
 - Added `notifications.overlayPosition` to place overlay notifications at the top left, top center, or top right; top right remains the default.
 - Added a notification history panel (default `Ctrl+N`, configurable via `shortcuts.toggleNotificationHistory`) that logs every notification shown during the session; the toggle works whether the overlay or mpv has focus, the panel slides in from the same edge as notifications (right when centered), and entries can be removed individually or cleared.
-- Made the overlay error/recovery toast follow the configured `notifications.overlayPosition` instead of always pinning to the top-right corner, and seeded the notification stack and history panel side from that position at startup.
-- Routed startup tokenization and subtitle annotation status through the configured notification surfaces; the bundled mpv plugin now only emits startup OSD messages for `osd` and `osd-system`.
-- Initialized the tray and visible overlay shell before deferred tokenization warmups finish on cold managed background startup, while keeping playback paused until SubMiner reports autoplay readiness.
+- Made the overlay error/recovery toast follow the configured `notifications.overlayPosition` instead of always pinning to the top-right corner, and kept the notification stack and history panel side synced from that position before first open so left-side history panels slide in from the left.
+- Routed startup tokenization, subtitle annotation, and character dictionary status through queued overlay notifications for `overlay`/`both` instead of falling back to mpv OSD while the overlay loads; queued loading cards are shown before their ready update when both happen before the overlay is ready, and the bundled mpv plugin now only emits startup OSD messages for `osd` and `osd-system`.
+- Preserved character dictionary checking/building/importing/ready phases in overlay notification history and sent those phases to system notifications when `notificationType` is `both`.
+- Initialized the tray and visible overlay shell before deferred tokenization warmups finish on visible-overlay startup, while keeping playback paused until SubMiner reports autoplay readiness.
 - Kept playback feedback such as subtitle visibility, subtitle track, and subtitle delay text on overlay/OSD surfaces only; desktop/system notifications are reserved for real notifications like mined cards, errors, and updates.
 - Reused the active primary/secondary subtitle mode overlay notification while cycling modes so rapid toggles update one card instead of stacking duplicate feedback.
 - Fixed mined-card overlay notifications so `overlay` and `both` modes show the same generated card thumbnail as system notifications.