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

scripts/publish-all.mjs

@@ -18,8 +18,7 @@ const dryRun = args.includes("--dry-run");
 const publishOrder = [
   "workflow-protocol",
   "workflow-util",
-  "workflow-moderator",
-  "workflow-agent-kit",
+  "workflow-util-agent",
   "workflow-agent-hermes",
   "workflow-agent-builtin",
   "cli-workflow",