MCP: PR creation form's branch is too wide

<img width="504" height="376" alt="Image" src="https://github.com/user-attachments/assets/e239c4c2-28a9-4164-9334-41f0476ca2a9" />

Version: 1.132.0-insider (Universal)
Commit: 54917b34eaaeeec2b294c43d691fc6c1e4b86c89
Date: 2026-07-29T16:40:29Z
Electron: 42.7.1
ElectronBuildId: 14760073
Chromium: 148.0.7778.280
Node.js: 24.18.0
V8: 14.8.178.38-electron.0
OS: Darwin arm64 25.5.0