refactor: extract @uncaged/workflow-util-agent + smart prompt

- New package: spawn-cli + build-agent-prompt shared utils
- Smart prompt: start + meta summaries for middle steps + last step full
- Cursor/Hermes adapters now import from util-agent (no duplicate code)
- 109 tests pass, biome clean

Closes #14
小橘 <xiaoju@shazhou.work>

packages/workflow-agent-cursor/tsconfig.json

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