feat(windows): restore project opening and title menu workflows

[Mucheen]

Summary

• add a consistent current-window/new-window choice for project opening and remember the selected preference
• add a macOS-style title project menu for switching open projects, reopening recent projects, and launching new/open/clone actions
• keep background Git operations from flashing a console and create additional app windows through an async Tauri command
• localize the new Windows workflows and remove the obsolete activity-rail project switcher

Testing

• bun test focused suite: 32 tests, 147 assertions
• bun run typecheck
• targeted vp lint for changed TypeScript files
• bun run build
• Rust Core cargo fmt --check
• targeted rustfmt --check for host.rs
• Rust Core comment verification
• Rust Git background-process regression test
• Tauri async window-command regression test