Summary

• Add Cmd/Ctrl+D to delete current line (configurable in settings)
• Add Alt+Up/Down to move current line up/down (configurable in settings)
• Fix line operations not working in Split mode (cursor position was being overwritten by rendered pane)
• Fix tooltips showing "Ctrl+E" instead of "Cmd+E" on macOS
• Add keyboard shortcut documentation
• Add i18n translations for new shortcut settings (en, de, ja, zh_Hans)

Details

Line Manipulation

New keyboard shortcuts for common editing operations:

• Delete Line: Removes the current line entirely, placing cursor at the same column on the next line
• Move Line Up/Down: Swaps the current line with the line above/below

Split Mode Fix

In Split mode, the rendered pane was overwriting tab.cursor_position after the raw editor set it. This caused line operations (delete line, move line) to operate on the wrong line when editing in the raw pane. Fixed by not updating cursor_position from the rendered pane in Split mode.

macOS Tooltip Fix

View mode tooltips were hardcoded to show "Ctrl+E" on all platforms. Now uses modifier_symbol() helper to show "Cmd+E" on macOS.

Test plan

• cargo build compiles successfully
• Test Delete Line (Cmd+D) in Raw mode
• Test Delete Line (Cmd+D) in Split mode - should delete line in left pane
• Test Move Line Up/Down (Alt+Arrow) in Raw mode
• Test Move Line Up/Down (Alt+Arrow) in Split mode
• Hover over view mode indicator - should show "Cmd+E" on macOS, "Ctrl+E" on other platforms