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

tsconfig.json

@@ -20,8 +20,7 @@
   "references": [
     { "path": "packages/workflow-util" },
     { "path": "packages/workflow-protocol" },
-    { "path": "packages/workflow-moderator" },
-    { "path": "packages/workflow-agent-kit" },
+    { "path": "packages/workflow-util-agent" },
     { "path": "packages/workflow-agent-hermes" },
     { "path": "packages/workflow-agent-builtin" },
     { "path": "packages/cli-workflow" }