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.

bruno/collections/set_chain_order.yml

@@ -0,0 +1,29 @@
+info:
+  name: Set Collection Chain Order
+  type: http
+  seq: 13
+
+http:
+  method: PUT
+  url: '{{base_url}}/api/collections/{{collection_id}}/view-settings'
+  auth: inherit
+  body:
+    type: json
+    data: |-
+      {
+        "chain_order": "newest"
+      }
+settings:
+  encodeUrl: true
+  timeout: 0
+  followRedirects: true
+  maxRedirects: 5
+
+docs:
+  content: |-
+    # Set Collection Chain Order
+
+    `PUT /api/collections/:id/view-settings` — auth: jwt.
+
+    Canonical reference: docs/developer/api/collections/set_chain_order.md (docs site → Developer → API). This request is GENERATED from that doc; edit the doc, then run the drift test with -update.
+  type: text/markdown