Tiles view: focus/zoom a single tile to full-screen (and back)

The tiles view for running parallel sessions is great, but there's no way to temporarily expand one tile to full screen to read or interact with it closely, then collapse back to the grid without losing the layout.

Requested: a "focus" / maximize toggle on each tile — e.g. double-click the tile header, a hover button, or a dedicated keyboard shortcut (picking keys that don't collide with existing shortcuts like Cmd+Enter / Esc). The other sessions keep running in the background; returning restores the exact tile arrangement.

Why: I frequently need to dig into one session momentarily without tearing down my parallel setup. Today the small tile makes close reading/editing awkward, and there's no quick zoom-and-return.