docs(api): sync mirrors with the retired rules CRUD and the chain-order endpoint

Three mirrors had drifted:

- The rules-endpoint retirement (4f71eda6) deleted the routes but not
  their mirrors: removed docs/developer/api/collections/
  {add_auto_assign_rule,remove_auto_assign_rule,test_rule,update_rule}
  .md + their bruno twins, and pruned /api/collections/test-rules,
  /{id}/rules, /{id}/rules/{ruleId} from the generated openapi spec
  (hand-edited — regenerating with -update would wipe hand-authored
  bruno suites that predate the docs mirrors).
- New endpoint PUT /api/collections/:id/view-settings gets a doc page
  + schema-registry entry + bruno mirror (repo convention: the route
  and its docs land together).
- 54 pre-existing TestDocsMatchRoutes failures: the media-item
  endpoints emit the 16 episode/download fields (source_feed_id,
  feed_position, download_state, enclosure_url, hosts/guests, …) and
  libraries emit purpose/allow_member_feeds, but the doc examples
  were never extended — the package only runs on the host, so the
  container suite never caught it. Examples now carry every key the
  handlers emit; internal/docs is fully green.

docs/developer/openapi.yaml

@@ -277,33 +277,6 @@ paths:
       responses:
         '200':
           description: Success
-  "/api/collections/test-rules":
-    post:
-      tags: [collections]
-      summary: "Test Rule"
-      security:
-        - bearerAuth: []
-      requestBody:
-        content:
-          application/json:
-            example: |-
-              {
-                "rules": [
-                  {
-                    "field": "genre",
-                    "operator": "equals",
-                    "value": "Science Fiction"
-                  },
-                  {
-                    "field": "author",
-                    "operator": "contains",
-                    "value": "Asimov"
-                  }
-                ]
-              }
-      responses:
-        '200':
-          description: OK
   "/api/collections/{id}":
     delete:
       tags: [collections]
@@ -409,38 +382,10 @@ paths:
       responses:
         '200':
           description: Success
-  "/api/collections/{id}/rules":
-    post:
-      tags: [collections]
-      summary: "Add Auto-Assign Rule"
-      security:
-        - bearerAuth: []
-      requestBody:
-        content:
-          application/json:
-            example: |-
-              {
-                "field": "genre",
-                "operator": "equals",
-                "value": "Science Fiction",
-                "priority": 1,
-                "enabled": true
-              }
-      responses:
-        '201':
-          description: Created
-  "/api/collections/{id}/rules/{ruleId}":
-    delete:
-      tags: [collections]
-      summary: "Remove Auto-Assign Rule"
-      security:
-        - bearerAuth: []
-      responses:
-        '204':
-          description: No Content
+  "/api/collections/{id}/view-settings":
     put:
       tags: [collections]
-      summary: "Update Collection Rule"
+      summary: "Set Collection Chain Order"
       security:
         - bearerAuth: []
       requestBody:
@@ -448,11 +393,11 @@ paths:
           application/json:
             example: |-
               {
-                "enabled": false
+                "chain_order": "newest"
               }
       responses:
         '200':
-          description: Success
+          description: OK
   "/api/conflicts":
     get:
       tags: [conflicts]