v0.8.45: /model change reverts when picker is dismissed with Esc

[Hmbown]

Problem

Using /model to change the active model, then pressing Esc to close the picker, reverts the model to its previous value. The change only persists when you explicitly press Enter or click to confirm.

Desired behavior

• Selecting a model in the picker (scrolling to it) should count as a selection
• Pressing Esc should close the picker but keep the last-highlighted/selected model
• The model footer indicator should update to reflect the last selection
• If no selection was ever made (picker opened and immediately Esc'd), keep the current model

Acceptance criteria

• Model picker: Esc keeps the last focused model
• Model picker: opening and immediately closing with Esc keeps current model
• Model change is reflected in footer after Esc dismiss
• Test: open picker, scroll, Esc → model is updated