Adds Z as a keyboard equivalent for the existing double-click zoom-to-team
gesture (WCAG 2.1.1). When a team node is selected, pressing Z dispatches
molecule:zoom-to-team, which fitBounds to the parent and all children.
Input elements are guarded so Z still types normally in text fields.
Adds a 6th help panel entry documenting the Dbl-click / Z gesture.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>