Backfill YouTube titles through the queue

CURRENT.md

@@ -40,6 +40,15 @@ mobile draft at 390px.
   - [x] C11 preview caching: Discord-hosted image/GIF previews (WebP 320px, hash-addressed, 5 MiB
     cap, one attempt) run after every walk in both modes. Live run `...-20260916090722`:
     `previewed: 2`; thumbs served over `/api/media/<scrape>/<item>/thumb` (200).
+  - [x] C50 Title backfill in the queue. YouTube-like rows (provider or URL matching
+    youtube/youtu.be) without a title are now a second work type in the backfill queue: resolved
+    through the provider oEmbed, stored as `title`/`title_key`, with `title_attempts` and
+    `title_error` so deleted videos close out after the tries setting. Titles and previews share a
+    batch (up to half for titles while both remain); `previewCounts().titlePending`,
+    `BackfillMember.pendingTitles`, and the job totals carry the work, and the Bot tab member line
+    shows `+ N titles`. Unit tests cover selection, resolution, and the give-up cap. Live: the
+    user's queue (batch 40, 30 s, auto off) started once to verify — 133 titles resolved in two
+    minutes, dead videos counting toward the cap.
   - [x] C49 Searchable video titles. Embed rows now store Discord's `title` plus a normalized
     `title_key` (lowercase, punctuation collapsed). The Advanced drawer has a title field with an
     **Exact match (quotes)** toggle: default is order-free multi-word prefix search ("Ma Ca Ju"