fix: 修复 GitHub Actions release workflow 权限问题 (#119)

将触发事件从 pull_request 改为 push，解决来自 fork 的 PR 合并时
因权限受限导致的 403 错误。

- 触发条件：从 pull_request(closed) 改为 push to main
- 条件判断：相应调整为 push 事件的判断逻辑

这样可以确保 workflow 在代码真正合并到 main 分支后才运行，
此时有完整的 contents:write 权限来创建 release。

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

Co-authored-by: Claude <noreply@anthropic.com>

.github/workflows/release.yml

@@ -1,8 +1,7 @@
 name: Build and Release
 
 on:
-  pull_request:
-    types: [closed]
+  push:
     branches: [ main ]
   workflow_dispatch:
 
@@ -12,8 +11,8 @@ permissions:
 jobs:
   build:
     runs-on: ubuntu-latest
-    # 只在 PR 被合并时运行，或手动触发
-    if: (github.event.pull_request.merged == true) || (github.event_name == 'workflow_dispatch')
+    # 只在推送到 main 时运行，或手动触发
+    if: (github.event_name == 'push' && github.ref == 'refs/heads/main') || (github.event_name == 'workflow_dispatch')
 
     steps:
     - uses: actions/checkout@v4