🤖 feat: add fetch-latest option for workspace creation

[kylecarbs]

Generated with mux

Summary

• Added a persisted "Fetch latest" checkbox to the workspace creation controls so new workspaces can start from the freshest remote state
• Plumbed the fetchLatest flag through IPC, runtime APIs, and frontend settings; LocalRuntime now branches from origin/<trunk> after fetching, while SSHRuntime fetches, fast-forwards the trunk when safe, then bundles
• Added integration tests covering both local and SSH runtimes to verify new branches match remote HEAD when the option is enabled

Testing

• make typecheck
• TEST_INTEGRATION=1 bun x jest tests/ipcMain/createWorkspace.test.ts -t "bases new workspace branch on origin head when fetchLatest is enabled" (passes)