feat: Phase 3 — engine read path + runtime context builder

- Add buildThreadContext(headHash, cas) to workflow-runtime
- Expand extract phase to return { meta, contentPayload, refs[] }
- Add parseCasThreadNode() to workflow-cas for node type parsing
- Update createWorkflow to write ContentMerkleNode with artifact refs
- Tests: 4 pass (build-context + extract-refs)
- Biome format pass on all files

Refs #155, closes #158

小橘 <xiaoju@shazhou.work>

packages/workflow-template-develop/tsconfig.json

@@ -6,8 +6,5 @@
     "composite": true
   },
   "include": ["src/**/*.ts"],
-  "references": [
-    { "path": "../workflow-register" },
-    { "path": "../workflow-runtime" }
-  ]
+  "references": [{ "path": "../workflow-register" }, { "path": "../workflow-runtime" }]
 }