ui: reveal the collapsed sidebar from its logo and toggle it there (#31307)
* ui: reveal the collapsed sidebar from its logo and toggle it there
The collapsed sidebar now shows only the logo; hovering it reveals the
icon strip until the pointer leaves. The expanded sidebar drops its
top-right collapse button and the logo collapses it on hover instead.
Assisted-by: Claude (Opus 5.5 Medium)
* ui: fade the peeked sidebar in at full width and keep the toggle slide
Hovering the logo of the collapsed sidebar now fades in the fully open
sidebar, floating over the page at its full width, instead of resizing
it. Opening or closing with the toggle still resizes and slides: the
sidebar docks to strip width while it slides, then floats out of sight,
and it stays hidden under the pointer after a toggle close. The unused
icon-only strip is removed from the sidebar actions.
Assisted-by: Claude (Opus 5.5 Medium)
* ui: stack the sidebar above the chat tabs on desktop
The peeked sidebar floats over the page, but the chat tab bar shared its
z-index and came later in the page, so the tabs were drawn on top of it.
Assisted-by: Claude (Opus 5.5 Medium)