External Editor Experience

What changed: External editors now launch in alternate screen buffer for cleaner terminal experience

Details:

• Added AAQ() function that wraps editor invocation with terminal screen switching
• Uses \x1B[?1049h to enable alternate screen before launching editor
• Uses \x1B[?1049l to restore original screen after editor exits
• Prevents editor output from polluting the Claude Code interface
• Cleans up temporary files after editor closes
• Supports $VISUAL, $EDITOR, and fallback editors (code, vi, nano)
• Evidence: AAQ() at line 422356 in v2.0.10 (screen buffer codes existed but not integrated in v2.0.9)