feat: port release-v2 experience improvements from PR #6582

Brings the semantically-correct unification work from the closed
agent/release-v2-experience PR into release/v2:

- universal create surface (header, board, spotlight) with permission-aware actions
- board empty state and setup checklist with widget/connection recipes
- in-widget integration editing via inspector modal, preserving unsaved widget settings
- single-source widget-integration capability map (nativeFeatureCapabilities)
- multi-endpoint Docker singleton with per-endpoint failure isolation, DOCKER_ENDPOINTS descriptors and service reconciliation
- Kubernetes multi-context registry with availability probing and context selector
- response-contract test harness and setup analytics property boundaries

Excludes the feature-platform generator/workbench tooling (deferred).

apps/docs/static/api/open-api-schema.json

@@ -1266,9 +1266,15 @@
                   "properties": {
                     "boardId": {
                       "type": "string"
+                    },
+                    "name": {
+                      "type": "string"
+                    },
+                    "layoutId": {
+                      "type": "string"
                     }
                   },
-                  "required": ["boardId"],
+                  "required": ["boardId", "name", "layoutId"],
                   "additionalProperties": false
                 }
               }