docs(book-matching,collections): Beam batch 10 — 15 endpoints

WO3 sync internals resolved: the book-matching docs ARE the sync surface
(books/query, link-book, bulk/auto-link, unlinked-books, suggestions,
file-alias CRUD) + collections rule/test/bulk-assign/shelf-mapping
surface.

Dedupe resolved (Claude call): search_books.md declared
GET /api/books/match but its BODY documents POST /api/sync/books/query —
both routes exist and are distinct (query-param device protocol vs JSON
body plugin protocol). Repointed search_books.md frontmatter to the POST
route; get_book_matches.md keeps the GET.

Claude registry: 15 entries (one pre-existing link-book entry deduped).
Drift fixed by gate: auto-link request {confidence_threshold, limit} not
{device_id, threshold}; bulk-link link objects {unlinked_book_id,
media_item_id, confidence_score} not {device_id, book_id, ...};
responses {results,total,successful,failed}/{auto_linked,results}; added
missing example-responses (bare delete, remove-rule is_smart-after
semantics, bulk-assign per-book results). make test 9/9.

docs/developer/api/book-matching/search_books.md

@@ -1,3 +1,11 @@
+---
+method: POST
+path: /api/sync/books/query
+auth: jwt
+area: book-matching
+---
+<!-- source: internal/handlers/matching.go:309 MatchingHandler.GetBookMatches -->
+
 # Search Books for Matching
 
 Query books to find potential matches for linking.
@@ -18,7 +26,7 @@ Query books to find potential matches for linking.
 
 ### Example Request
 
-```json
+```json example-request
 {
   "identifiers": ["isbn:978-0345391802", "uuid:abc-123"],
   "sha256": "a1b2c3d4e5f6abc123...",
@@ -30,7 +38,7 @@ Query books to find potential matches for linking.
 
 ## Response (200 OK)
 
-```json
+```json example-response
 {
   "matches": [
     {