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.

internal/docs/schema.go

@@ -601,6 +601,14 @@ var Schemas = map[string]Schema{
 		Request:  json.RawMessage(`{"item_ids": []}`),
 		Response: json.RawMessage(`{"status": "reordered"}`),
 	},
+	"PUT /api/collections/:id/view-settings": {
+		// Merges chain_order into the collection's view_settings JSONB
+		// (playlist toggles share the doc and are preserved).
+		Request: json.RawMessage(`{"chain_order": "newest"}`),
+		Response: json.RawMessage(`{
+			"id": "", "chain_order": "", "view_settings": {}
+		}`),
+	},
 	"PUT /api/collections/:id/rules/:ruleId": {
 		// Handler is SetRuleEnabled: toggle only, request {enabled required},
 		// response {collection_id, is_smart}.