feat: P4 qdrant collection lifecycle (self-heal + guarded rebuild)

- shared TS collection manager: self-heal creates missing collection (1024/cosine)
  and missing keyword payload indexes; never mutates incompatible contracts
  (semantic_index_incompatible); async index visibility polled with bounded deadline
- session admission (qdrantEnsure) uses the manager in self-heal mode; operator path
  keeps require_existing semantics
- runtime lease exposes semanticQdrantUrl to the operator
- operator commands vector-inspect/vector-rebuild with exact confirmation guards
- thothctl workspace vector inspect|rebuild (Go) with --collection/--confirm/--destroy
- p4 acceptance runner: real Qdrant (v1.18.2) lifecycle checks, 11/11 PASS
- docs: CLI contract, manual walkthrough P4 (PENDING), PROJECT_STATE

backend/src/runtime/readiness-manager.ts

@@ -46,7 +46,7 @@ export class ReadinessManager {
     const pending = (async (): Promise<ReadinessResult> => {
       try {
         if (descriptor) {
-          const qdrant = await runner.qdrantEnsure(descriptor, this.timeoutSec);
+          const qdrant = await runner.qdrantEnsure(descriptor, this.timeoutSec, "self_heal");
           if (!qdrant.ok) return qdrant;
         }
         const ollama = await runner.ollamaEnsure(workspace, this.timeoutSec);