fix(tui): cap inline image height and preserve multiplexer scrollback
Inline images (screenshots from puppeteer, assistant images) rendered at
unbounded height — a 1280x800 screenshot consumed ~32 terminal rows,
causing excessive scrolling. In multiplexers (tmux, screen, zellij),
this was compounded by fullRender clearing scrollback on every resize.
Image height cap:
- New setting tui.maxInlineImageRows (default 20)
- Effective cap: min(setting, floor(viewport * 0.6))
- Shared resolveImageOptions() replaces per-site settings reads
- Existing calculateImageFit() already handles maxHeightCells
Multiplexer scrollback preservation:
- Skip CSI 3J (clear scrollback) in tmux/screen/zellij
- Skip fullRender(true) on height change in multiplexers
- Cached isMultiplexer constant (TMUX, STY, ZELLIJ env vars)
Sam Biggins
cafcf906fd