fix: gate workspace diagnostic migration

docs/superpowers/specs/2026-08-03-git-workspace-registry-design.md

@@ -114,7 +114,7 @@ The initial canonical shape is:
 
 ```yaml
 workspace:
-  schema_version: 1
+  schema_version: 2
   id: psd-clinical
   name: Policlinico San Donato
   description: Clinical data warehouse workspace
@@ -132,6 +132,8 @@ dwh:
 semantic_index:
   vector_store:
     engine: pgvector
+    database: postgres
+    schema: vectors
     collection: clinical_documents
     dimensions: 768
     distance: cosine
@@ -153,7 +155,20 @@ llm_policy:
 
 The exact machine schema is maintained by `WorkspaceSchema` and versioned with explicit migrations. Unknown keys are rejected by default so misspellings do not silently change runtime behavior.
 
-### 6.1 Semantic-index invariant
+### 6.1 Version migration and operational state
+
+Schema version 2 makes `semantic_index.vector_store.database` and `.schema` mandatory. They
+identify the vector service independently of the DWH, even when both happen to use the same
+PostgreSQL instance.
+
+Version 1 descriptors remain readable and listable so operators can discover legacy Git content.
+They are marked `migration_required` and may not generate installation bindings, runtime
+configuration, diagnostics, or publication artifacts. Migration is an explicit UI/transformer
+action that supplies the vector database/schema; it must never infer either value from the DWH.
+The resulting descriptor is written as schema version 2 and then passes normal operational
+validation.
+
+### 6.2 Semantic-index invariant
 
 `semantic_index` is atomic. The vector collection, vector dimensions, distance metric, embedding provider, embedding model, and embedding dimensions describe one index contract.