Nathan feedback round 2:
- #3220: generated images were rendering at the 120x90 upload-thumbnail size
(too small for the subject of the message). Now render at natural aspect
ratio up to 360px (max-height 360, responsive max-width), lightbox preserved.
- #3223: drop the per-item subtitle/description lines from the session action
menu — show only icon + label (VS Code / browser / ChatGPT pattern). The
description is preserved as a hover tooltip (title=). Makes the menu ~40%
shorter, less crowded, and structurally less prone to viewport clipping.