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/collections/add_auto_assign_rule.md

@@ -1,3 +1,11 @@
+---
+method: POST
+path: /api/collections/:id/rules
+auth: jwt
+area: collections
+---
+<!-- source: internal/handlers/collections.go:877 CollectionHandler.AddRule -->
+
 # Add Auto-Assign Rule
 
 Add an automatic book assignment rule to a collection.
@@ -49,7 +57,7 @@ Add an automatic book assignment rule to a collection.
 
 ### Example Request
 
-```json
+```json example-request
 {
   "field": "genre",
   "operator": "equals",
@@ -61,15 +69,11 @@ Add an automatic book assignment rule to a collection.
 
 ## Response (201 Created)
 
-```json
+```json example-response
 {
-  "id": "rule-uuid-here",
-  "field": "genre",
-  "operator": "equals",
-  "value": "Science Fiction",
-  "priority": 1,
-  "enabled": true,
-  "created_at": "2026-02-01T10:00:00Z"
+  "collection_id": null,
+  "is_smart": null,
+  "rule": null
 }
 ```