Design for replacing the two-scalar layout (pty_pct + roster_width) with a
binary space-partition pane tree so every pane is resizable on both axes,
fixing the "only roster width adjusts" limitation. Rolls a small in-repo tree
(no new dep) and drives the PTY grid from the terminal pane's actual Rect.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
leetcrypt