docs(auth,devices): Beam WO5 batch 3 — 15 endpoints backfilled, registry pinned

Beam backfilled auth core (login/register/refresh/logout/profile) and devices
core (list/update/delete/shelf CRUD/sidecar/register flow) with frontmatter,
provenance, and labeled examples. All claimed shapes verified against
handlers: AuthResponse {access_token, refresh_token omitempty, token_type,
expires_in, user}, update device {device_updated, device}, shelf wrappers,
DeviceAuthStatusResponse.

Claude registry verification: 15 entries pinned by type (LoginRequest,
RegisterRequest, AuthResponse, RefreshTokenRequest/Response, UserProfile,
DeviceListResponse, DeviceUpdateRequest, AddToShelfRequest, SidecarConfig,
DeviceRegistrationRequest/Response, DeviceAuthStatusRequest/Response).
Removed revoke_device.md — name-only duplicate of delete_device.md (same
DELETE /api/devices/:id route; was the last audit-orphan doc).

Gate catches this round (subtle Go serialization facts, now pinned in docs):
- uuid.UUID arrays never serialize as omitted: register/status response
  ALWAYS carries device_id (all-zeros while pending) despite omitempty
- update device request binds device_name, not name
- register response includes device_id alongside registration_id
- list devices response is a {devices, total} wrapper

docs/developer/api/devices/clear_shelf.md

@@ -1,3 +1,11 @@
+---
+method: DELETE
+path: /api/devices/:id/shelves/clear
+auth: jwt
+area: devices
+---
+<!-- source: internal/handlers/media.go:413 MediaHandler.ClearShelf -->
+
 # Clear Shelf
 
 Remove all items from a device's shelf.
@@ -24,9 +32,14 @@ DELETE /api/devices/550e8400-e29b-41d4-a716-446655440000/shelves/clear
 Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...
 ```
 
-## Response (204 No Content)
+## Response (200 OK)
 
-Shelf cleared successfully.
+```json example-response
+{
+  "status": "success",
+  "message": "all shelves cleared"
+}
+```
 
 ## Error Responses