feat(orchestrator): observe Page Data validation

docs/architecture/memind-orchestrator-boundary.md

@@ -101,6 +101,7 @@ The framework-neutral contracts are:
 - `executor-job-request-v1`
 - `executor-job-state-v1`
 - `executor-dispatch-decision-v1`
+- `page-data-validation-observation-v1`
 
 The Phase 3.2 Executor Gateway owns the adapter registry and executor job state
 transition boundary. Requests contain workspace/artifact references,
@@ -155,6 +156,7 @@ The implemented internal API is:
 ```text
 POST /v1/runs
 GET /v1/runs/:id
+POST /v1/runs/:id/validation-observations
 POST /v1/runs/:id/resume
 POST /v1/runs/:id/cancel
 DELETE /v1/runs/:id
@@ -177,6 +179,16 @@ through `DELETE /v1/runs/:id`; deletion removes the LangGraph thread and its
 linked terminal Executor Job, whose events cascade in PostgreSQL. Active or
 waiting runs fail deletion with `409`.
 
+Page Data code runs may append a post-run
+`page-data-validation-observation-v1` after the Native delivery guards finish.
+The observation contains only bounded check identifiers, pass/fail/skipped
+states, error codes, and aggregate page/publication counts. User prompts, code,
+workspace paths, dataset contents, credentials, and database identifiers must
+not cross this boundary. The Orchestrator derives and checkpoints a
+`passed`/`failed`/`inconclusive` verdict and emits
+`workflow_validation_observed`. In the initial observation phase this verdict
+does not mutate the Native run result or publication state.
+
 The graph keeps three deterministic control-plane nodes:
 
 ```text