mecatui: make wrapped selectable lists height-aware

Problem

Selectable, scrolling mecatui lists budget logical entries before rendering. Some rows can now wrap to multiple physical terminal rows, so long dynamic values can exceed the reserved viewport height and push footer chrome out of view.

Affected families:

• Subagent, Parallel, and Team rosters
• Models picker
• Sessions list

Follow-up

Prepare rows at the final body width before selecting the visible window. Retain a logical-item to physical-row mapping so cursor movement remains item-based, the selected item remains visible, page navigation is coherent, and one-row chrome/footer reservations are preserved. Evaluate whether any list should intentionally remain single-line with semantic elision instead.

Context

Identified during PR #1105 panel review. Current behavior is accepted for that PR; do not fold this architectural scroll-window change into the card-layout correction.