Portrait rendering breaks on multi-monitor, window moves, and DPI changes

[arcaven]

Observed behavior

Multiple related portrait rendering issues, all stemming from terminal graphics protocol (Kitty/Sixel) interaction with WezTerm multi-monitor handling:

1. Starting a second forestage on another monitor erases the portrait from the first session
2. Moving a window between monitors erases the portrait (toggle on/off restores it)
3. On a different-resolution monitor, the portrait renders as a partial/cropped image
4. Size cycling in bottom position causes horizontal drift (small=far right, original=near center)

Root cause

• ratatui-image captures picker.font_size() once at startup
• Kitty protocol images stored in terminal graphics memory are invalidated by monitor/DPI changes
• Multiple instances may compete for graphics IDs
• Cell size calculations use stale font metrics after the display context changes

Fix direction

• Listen for terminal resize events and re-query font size from the picker
• Re-send image data after resize/move (force re-render)
• May need ratatui-image upstream support for resize-aware rendering

Priority

Low — these are edge cases that affect multi-monitor setups. The portrait is cosmetic and can be restored with Ctrl+P or Alt+P toggle. Core TUI functionality (text, input, conversation) is unaffected.

Environment

• Terminal: WezTerm
• OS: macOS (multi-monitor, different resolutions)
• ratatui-image 10.0, crossterm 0.29

[arcavenai]

Confirmed fixed in forestage f6cb783. Tested in wezterm on Wayland (Raspberry Pi 5, Debian 13). Resized the window, dragged it across multiple positions on the desktop — the portrait stays in its relative location and re-renders correctly each time. No tearing, no orphan rendering.