20260430 - v1.5.1

• New data-driven dialog system (quickui#dialog#open): supports 7 control types — label, input, radio, checkbox, button, separator, and dropdown
• System cursor hiding: new hide_system_cursor option for context menu and listbox to hide the terminal cursor while popup is active
• Readline fixes: correct CJK width calculation, visual selection clearing, cursor blink timing, slide window bounds, and Ctrl-C copy behavior
• Bug fixes: fixed buffer swapfile option, expand_text() typo, getchar() busy loop, and match_ft() blacklist/whitelist parsing
• Documentation: added DIALOG.md user guide, internal module reference docs, and dialog test suite