Under the hood
Terminal viewport sizing can now reserve columns for a side pane
What
The hook that manages the terminal viewport's dimensions now accepts a third parameter specifying a number of columns to reserve. It computes a conversationColumns value equal to the total terminal columns minus the reserved amount (with a minimum of 1), and uses this reserved-aware value for its resize-debounce logic instead of the raw terminal column count.
Why
This lets the terminal layout set aside horizontal space for a side pane without that space affecting how the main conversation area is sized or how resizing is handled.