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

CONTRIBUTING.md

@@ -94,8 +94,7 @@ This creates a markdown file in `.changeset/` describing the change. It will be
 packages/
   workflow-protocol/      # Shared types and JSON Schema
   workflow-util/          # Encoding, IDs, logging, frontmatter
-  workflow-moderator/     # Status-based graph evaluator
-  workflow-agent-kit/     # createAgent factory, extract pipeline
+  workflow-util-agent/    # createAgent factory, extract pipeline
   workflow-agent-hermes/  # Hermes ACP agent
   workflow-agent-builtin/ # Built-in LLM agent
   workflow-agent-claude-code/ # Claude Code agent