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/get_unlinked_book_suggestions.md

@@ -1,3 +1,11 @@
+---
+method: GET
+path: /api/sync/unlinked-books/:id/suggestions
+auth: jwt
+area: book-matching
+---
+<!-- source: internal/handlers/book_matching.go:392 Handler.GetUnlinkedBookSuggestions -->
+
 # Get Unlinked Book Suggestions
 
 Get suggested matches for unlinked books on a device.
@@ -33,7 +41,7 @@ Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...
 
 ## Response (200 OK)
 
-```json
+```json example-response
 {
   "suggestions": [
     {
@@ -44,18 +52,27 @@ Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...
         {
           "media_item_id": "uuid",
           "title": "Foundation",
-          "authors": ["Isaac Asimov"],
+          "authors": [
+            "Isaac Asimov"
+          ],
           "confidence": 0.95
         },
         {
           "media_item_id": "uuid-2",
           "title": "Foundation and Empire",
-          "authors": ["Isaac Asimov"],
+          "authors": [
+            "Isaac Asimov"
+          ],
           "confidence": 0.75
         }
       ]
     }
-  ]
+  ],
+  "action": null,
+  "sha256": null,
+  "title_from_device": null,
+  "total_suggestions": null,
+  "unlinked_book_id": null
 }
 ```