Docking a modal to a window edge pushes the chat aside (body padding via
right-dock-active + --right-dock-w). Three problems on close/reopen:
1. Chat stayed offset after closing a docked modal. The close-watcher only
reacted to the `.hidden` class or DOM removal, but the draggable modals
(calendar, plan, workspace, document, …) close via inline `display:none`.
Watch the `style` attribute too and treat `display:none` as closed.
2. Reopening a previously-docked singleton modal floated it off to the side,
overlapping the chat. The reused element kept its docked inline geometry.
Clear the content's inline position/size on close so it reopens at its CSS
default (centered).
3. Undock wasn't animated. The transition lived on `.right/left-dock-active`,
so removing the class dropped the transition with it and padding snapped to
0. Move the transition to the base `body` so the push animates both ways.
Files: static/js/modalSnap.js, static/style.css.
Checks: node --check static/js/modalSnap.js; verified in-browser (dock → close
→ chat animates back; reopen → centered, no overlap).
