Resolve the session-selector.ts conflict by integrating the delete-dialog
content-slot fix (#3283) on top of the fullscreen mouse-picker refactor.
The branch swapped the delete-confirmation dialog INTO a single content
slot (replacing the SessionList) so the picker is always
`chrome + max(list, dialog) + chrome` and never overflows the viewport.
Adjustments baked into this merge:
- Wrap the SessionList in `#contentSlot` and keep the dialog swapping into
that slot, but preserve the new fullscreen path: mouse hit-testing,
the pinned footer (`#footerLines`/`#footerStart`), and fill-height
trimming all still work because the render offset now tracks
`#contentSlot` (the list lives one level down).
- Keep both CHANGELOG entries (picker mouse/fullscreen + #3283 fix) and
the ported scroll-stability regression test.
can1357
92d03466b7