- Add Focusable interface for components that need hardware cursor positioning
- Add CURSOR_MARKER (APC escape sequence) for marking cursor position in render output
- Editor and Input components implement Focusable and emit marker when focused
- TUI extracts cursor position from rendered output and positions hardware cursor
- Track hardwareCursorRow separately from cursorRow for differential rendering
- visibleWidth() and extractAnsiCode() now handle APC sequences
- Update overlay-test.ts example to demonstrate Focusable usage
- Add documentation for Focusable interface in docs/tui.md
Closes#719, closes#525
07fad1362c