Phase 28-36 body of work

Accumulated since a6f12e2 (Phase 21 Rust port + Phase 27 versioning):

- Phase 36: embed_semaphore on VectorState (permits=1) serializes
  seed embed calls — prevents sidecar socket collisions under
  concurrent /seed stress load
- Phase 31+: run_stress.ts 6-task diverse stress scaffolding;
  run_e2e_rated.ts + orchestrator.ts tightening
- Catalog dedupe cleanup: 16 duplicate manifests removed; canonical
  candidates.parquet (10.5MB -> 76KB) + placements.parquet (1.2MB ->
  11KB) regenerated post-dedupe; fresh manifests for active datasets
- vectord: harness EvalSet refinements (+181), agent portfolio
  rotation + ingest triggers (+158), autotune + rag adjustments
- catalogd/storaged/ingestd/mcp-server: misc tightening
- docs: Phase 28-36 PRD entries + DECISIONS ADR additions;
  control-plane pivot banner added to top of docs/PRD.md (pointing
  at docs/CONTROL_PLANE_PRD.md which lands in next commit)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/catalogd/src/grpc.rs

@@ -54,7 +54,16 @@ impl CatalogService for CatalogGrpc {
         let manifest = self.registry
             .register(req.name, SchemaFingerprint(req.schema_fingerprint), objects)
             .await
-            .map_err(|e| Status::internal(e))?;
+            .map_err(|e| {
+                // Mirror the HTTP side's 409 mapping: schema drift is a
+                // precondition failure, not a server error. Keeps gRPC
+                // and HTTP callers seeing the same diagnostic signal.
+                if e.contains("different schema") {
+                    Status::failed_precondition(e)
+                } else {
+                    Status::internal(e)
+                }
+            })?;
 
         Ok(Response::new(manifest_to_proto(&manifest)))
     }