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-util-agent/__tests__/context.test.ts

@@ -0,0 +1,14 @@
+import { describe, expect, test } from "vitest";
+
+// We need to test buildHistory indirectly through buildContext
+// since buildHistory is not exported. For now, we'll test the integration
+// through the public API in a separate integration test.
+
+describe("context module - content extraction", () => {
+  test("placeholder - content extraction will be tested via integration tests", () => {
+    // This test is a placeholder. The actual testing of content extraction
+    // will be done through integration tests in build-continuation-prompt.test.ts
+    // where we can verify that StepContext objects have the correct content field.
+    expect(true).toBe(true);
+  });
+});