Introduce a reusable SelectMenu component and replace native select
controls across the UI. This centralizes select behavior and styling,
enabling grouped options, placeholders, and a consistent popup
interaction. Add comprehensive CSS and light-theme tweaks, and update
rebase action styling to integrate the new control.
- Add a unified SelectMenu component and wire change handlers.
- Implement .select-menu styles, popup behavior, and theme overrides.
- Replace ad-hoc native selects in dialogs and rebase UI for consistency.
Adds a new external tools subsystem to detect and launch
diff and editor tools across Windows, macOS, and Linux.
It exposes data models for tools, commands, and results to the UI
and serializes them for consumption by the app.
- Implement cross-platform discovery of editors and diff tools
- Expose serialized results to the UI for user selection
- Centralize per-OS known tool lists and overrides