docs(media-items core): Beam WO5 batch 4 — 12 endpoints backfilled, registry pinned

Beam backfilled list/get/create/update/delete media-item, search, ratings
CRUD, progress GET/PUT. Beam correctly identified create/update/delete as
jwt+admin (admin group in the router — verified).

Claude registry: 12 entries. Notable pins:
- get_media_item: hand-built ~44-key map pinned verbatim from the handler
- create/update return the full database.MediaItems row (74 columns) —
  examples merged up to the real shape via gate-driven merge script
- search returns []SearchMediaItemsRow (sqlc row — Real type pinned)
- rating scale is 1-10 int (odd = half-star); GET returns {rating: null} when
  absent; update reuses the create handler (201)
- progress GET: 25 base keys + 4 CONDITIONAL position-authority keys
  (css_selector/anchor_href/char_offset/context_text — added by the handler
  for convertible formats with a valid CFI); PUT progress binds
  sync.SaveProgressRequest and returns database.ReadingProgress
- Beam's examples were missing entirely on 4 files (list/search/progress
  GET/PUT) — relabeled existing fences or inserted contract-shaped blocks

Gate-driven merge scripts (object + array variants) brought all examples to
the exact handler key sets. make test 9/9.

docs/developer/api/media-items/list_media_items.md

@@ -1,3 +1,11 @@
+---
+method: GET
+path: /api/media-items
+auth: jwt
+area: media-items
+---
+<!-- source: internal/handlers/media.go:757 MediaHandler.ListMediaItems -->
+
 # List Media Items
 
 Retrieve a paginated list of media items, scoped to a library or across all libraries.
@@ -41,7 +49,7 @@ The response body is `{"data": [...]}` in both modes. The item shape differs by
 
 Nullable columns serialize as `null`.
 
-```json
+```json example-response
 {
   "data": [
     {