docs(kobo,koreader,collections): Beam WO5 batch 6 — 12 endpoints

Kobo emulation + KOReader calibre-compatible surface backfilled with
device-token auth; collections reorder + update_rule created.

Claude registry: 12 entries. kobo/koreader emulation endpoints all bind
arbitrary protocol POST bodies (markup/bookmark/gettests/sync-from-server,
koreader progress/bookmarks) — registered as AnyJSONObject, not bodyless as
first drafted. Initialization returns the library sync payload, not the init
response.

Contract correction in update_rule.md: the route is SetRuleEnabled ({enabled}
required -> {collection_id, is_smart}); Beam's draft invented rule-field
updates. Reordered response/status: {item_ids} -> {status: reordered}.

make test 9/9.

docs/developer/api/collections/reorder_items.md

@@ -0,0 +1,47 @@
+---
+method: PUT
+path: /api/collections/:id/items/order
+auth: jwt
+area: collections
+---
+<!-- source: internal/handlers/collections.go:1332 CollectionHandler.ReorderItems -->
+
+# Reorder Collection Items
+
+Applies a static collection's manual playlist order. Owner-only; the payload
+is the COMPLETE ordered id list — ids omitted keep their relative order
+appended after (the service never deletes membership).
+
+## Example request
+
+```json example-request
+{
+  "item_ids": [
+    "550e8400-e29b-41d4-a716-446655440000",
+    "660e8400-e29b-41d4-a716-446655440001"
+  ]
+}
+```
+
+## Example response
+
+```json example-response
+{
+  "status": "reordered"
+}
+```
+
+## Fields
+
+| Field | Type | Required | Notes |
+| ----- | ---- | -------- | ----- |
+| item_ids | array of string (uuid) | Yes | Complete ordered list of media item ids |
+
+## Errors
+
+| Status | Body | When |
+| ------ | ---- | ---- |
+| 400 | `{"error": "item_ids must be a non-empty ordered id list"}` / `{"error": "invalid media item id: ..."}` | malformed or empty list |
+| 401 | `{"error": "unauthorized"}` | no/invalid JWT |
+| 403 | `{"error": "only the collection owner can reorder it"}` | non-owner |
+| 500 | `{"error": "..."}` | unexpected server error |