Crush TUI overlaps sidebar and leaves spinner garbage (Windows, works outside rmux)

rmux 0.10.0, native Windows, attached session in Windows Terminal / PowerShell 7.

Full-screen TUI app: Crush v0.90.0 (Charm / Bubble Tea / Ultraviolet, alt screen).

What happens

Inside rmux the Crush UI falls apart while it is streaming:

• long lines (especially the highlighted “thinking” / reasoning block) wrap wrong and paint over the right sidebar and older messages
• frames stack on top of each other instead of replacing the previous one
• the working spinner leaves leftover junk on screen, e.g. 4*E5D2$4=1)£Dfb sitting next to Thinking

It looks like rows are not fully cleared / clipped to the pane, so old cells and over-wide lines stay visible.

Screenshot (attached).

What does not happen

Same Crush, same machine, same Windows Terminal, plain pwsh (no rmux) — layout is fine. No overlap, no leftover spinner glyphs.

So this is not Crush being generally broken on this box. It only shows up under rmux.

TERM is xterm-256color in both cases.

How to reproduce

1. Windows, rmux 0.10.0, attach a session in Windows Terminal.
2. Run crush in that pane (full-screen TUI).
3. Send a short message to a model that streams a reasoning / thinking block (I used Kimi K3; any long highlighted thinking dump should do).
4. Watch while it streams: thinking text spills into the sidebar, previous messages get overwritten, spinner glyphs stick around.

Outside rmux, same steps look normal.

Notes

This feels close to #217 (trailing cells emitted as real spaces, EL / erase-to-EOL only used in a few cases). Crush redraws a lot during thinking + spinner