feat: add MSW for mocking GitHub API in tests (#90)

This commit sets up Mock Service Worker (MSW) for comprehensive GitHub API mocking in tests, replacing manual jest.mock patterns with realistic network-level mocks.

## Changes

### Core Testing Infrastructure
- **src/test/msw-setup.ts**: MSW server setup with lifecycle hooks
- **src/test/github-handlers.ts**: 35+ GitHub API endpoint handlers
- **src/test/README.md**: Comprehensive documentation and usage guide

### Test Suite
- **src/gh.spec.ts**: Full test coverage for gh and ghc clients
  - 35 tests covering all major GitHub API operations
  - Tests for repos, pulls, issues, git, and users APIs
  - Cache behavior tests for ghc wrapper
  - Error handling tests (404, rate limits)

### Configuration
- **bunfig.toml**: Added MSW setup to test preload
- **package.json**: Added msw@^2.11.6 as dev dependency

## Coverage

All GitHub API endpoints used in the codebase:
- **Repos**: get, createFork, getBranch, listTags, getCommit, listReleases, webhooks
- **Pulls**: list, get, create, update, requestReviewers, listReviewComments
- **Issues**: list, get, update, comments, labels, timeline
- **Git**: getTag, deleteRef
- **Users**: getAuthenticated, getByUsername

## Benefits

1. **Realistic mocking**: Tests actual HTTP requests, not module implementations
2. **Type safety**: Full TypeScript support with Octokit types
3. **Centralized**: Single source of truth for mock data
4. **Maintainable**: Easy to add new endpoints
5. **Transparent**: Existing tests continue to work

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <[email protected]>

Author: snomiao

.env.test

@@ -7,7 +7,7 @@ FORK_OWNER=ComfyNodePRs
 FORK_PREFIX=PR-
 
 # Use docker compose up to get this mongodb before test
-MONGODB_URI=mongodb://localhost:27017
+# MONGODB_URI=mongodb://localhost:27017
 
 # @deprecated
 REPO=https://github.com/snomiao/ComfyNode-Registry-test

bun.lock

@@ -1,4 +1,4 @@
 preload = ["./src/preload.ts"]
 
 [test]
-preload = ["./src/preload.ts"]
+preload = ["./src/preload.ts", "./src/test/msw-setup.ts"]

bunfig.toml

@@ -182,6 +182,7 @@
     "eslint-config-next": "15.1.4",
     "husky": "^9.1.7",
     "lint-staged": "^16.1.2",
+    "msw": "^2.11.6",
     "next": "^15.4.1",
     "postcss": "^8.4.40",
     "prettier-plugin-organize-imports": "^3.2.4",