i'm not yet convinced i have the best heuristics for what to highlight,
but this feels like a useful step towards something a bit easier to
read, esp. when the model is producing large commands.
<img width="669" height="589" alt="Screenshot 2025-09-03 at 8 21 56 PM"
src="https://github.com/user-attachments/assets/b9cbcc43-80e8-4d41-93c8-daa74b84b331"
/>
also a fairly significant refactor of our line wrapping logic.
when the pager is scrolled to the bottom of the buffer, keep it there.
this should make transcript mode feel a bit more "alive". i've also seen
some confusion about what transcript mode does/doesn't show that i think
has been related to it not pinning scroll.
This fixes a bug where if you ran /diff while at turn was running,
transcript lines would be added to the end of the diff view. Also,
refactor to make this kind of issue less likely in future.
