Add new navigation and editing capabilities to improve data entry and
browsing efficiency.
- Implement `PageScroll` command for PageUp/PageDown navigation.
- Implement `OpenRecordRow` command (Vim-style 'o') to add a row and enter edit
mode.
- Implement `CommitAndAdvanceRight` command for Excel-style Tab navigation.
- Add keybindings for Home, End, PageUp, PageDown, and Tab.
- Update UI hints to reflect new Tab functionality.
Co-Authored-By: fiddlerwoaroof/git-smart-commit (unsloth/gemma-4-31B-it-GGUF:UD-Q5_K_XL)