refactor: rename workflow-agent-kit → workflow-util-agent, merge workflow-moderator into cli-workflow

- Rename packages/workflow-agent-kit → packages/workflow-util-agent
- Update all imports, tsconfig references, docs
- Delete dead file packages/workflow-util-agent/src/build-agent-prompt.ts
- Merge workflow-moderator (62 LOC) into cli-workflow/src/moderator/
- Move workflow-moderator to legacy-packages/
- Add mustache dependency to cli-workflow
- Update publish-all.mjs

Fixes #512

packages/workflow-agent-builtin/package.json

@@ -23,7 +23,7 @@
   },
   "dependencies": {
     "@uncaged/json-cas": "^0.5.2",
-    "@uncaged/workflow-agent-kit": "workspace:^",
+    "@uncaged/workflow-util-agent": "workspace:^",
     "@uncaged/workflow-util": "workspace:^"
   },
   "devDependencies": {