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-claude-code/__tests__/claude-code.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, test } from "bun:test";
-import type { AgentContext } from "@uncaged/workflow-agent-kit";
+import type { AgentContext } from "@uncaged/workflow-util-agent";
 import type { ThreadId } from "@uncaged/workflow-protocol";
 import { buildClaudeCodePrompt } from "../src/claude-code.js";