feat(KB-313): add task comments and merge details

- Add TaskComment and TaskCommentInput types to core
- Add MergeDetails type for tracking merge information
- Implement addTaskComment and list task comments in store
- Add comment API routes (/api/tasks/:id/comments)
- Add comment UI components in dashboard task modal
- Add CLI commands: kb task comment and kb task comments
- Include merge details display in task detail view
- Add tests for comment functionality

packages/engine/src/executor.test.ts

@@ -41,6 +41,8 @@ import { generateWorktreeName, slugify } from "./worktree-names.js";
 import type { Column, Task, TaskDetail } from "@fusion/core";
 
 const mockedCreateHaiAgent = vi.mocked(createKbAgent);
+const mockedGenerateWorktreeName = vi.mocked(generateWorktreeName);
+const mockedFindWorktreeUser = vi.mocked(findWorktreeUser);
 
 function createMockStore() {
   const listeners = new Map<string, Function[]>();