* feat(web): double-click tab to toggle maximize
Adds a dblclick gesture on dockview tabs that toggles maximize/restore on
the containing group, mirroring the existing maximize button. Preview tabs
keep their promote-to-pin shortcut: first dblclick pins, then dblclick
maximizes. Sidebar group is excluded.
* fix(web): add cursor-pointer to tab wrappers for consistency
* fix(web): add cursor-pointer to plan-tab wrapper
* fix(web): make tab dblclick maximize resilient to layout rebuild
Refactor the dblclick-to-maximize handler so it reads the panel's group ID
and store state at call time instead of from a render-time closure, and
guards against firing while the dockview store is mid-layout-restore.
This addresses oscillation when double-clicking a session tab on a task
that has multiple sessions: the maximize call now stops event propagation,
respects isRestoringLayout, and always uses the live api.group.id, so it
remains correct even after dockview rebuilds groups via fromJSON.
João Salavisa