feat: reset layer gives every clickable control a pointer cursor (and not-allowed when disabled) #549

Atlas app shipped clickable tiles (role=button, summary, label[for]) showing the arrow cursor. The lib reset (reset.css, @layer ca.reset) only has font: inherit; cursor: pointer is hand-written per component, so any new clickable element is wrong by default.

Plan: @layer ca.reset rule: pointer for button:not(:disabled), [role=button|tab|option|menuitem*|switch|checkbox|radio|link] (not aria-disabled), summary, label[for], a[href]; not-allowed for disabled / aria-disabled. App CSS (unlayered) wins freely. Dev check (devWarn) for click handler on a non-interactive element with cursor:auto: judged for noise before shipping.