- Implement `focus_panel` to programmatically switch between panels with validation.
- Add key bindings for `Ctrl+1`‑`Ctrl+5` to focus Files, Chat, Code, Thinking, and Input panels respectively.
- Update pane headers to display focus shortcuts alongside panel labels.
- Extend UI hint strings across panels to include the new focus shortcuts.
- Refactor highlight style handling and introduce a dedicated `highlight_style`.
- Adjust default theme colors to use explicit RGB values for better consistency.