Label and checkmark stack in one grid cell (inline-grid, grid-area 1/1,
checkmark visibility-hidden until .ok), so the button width is static by
construction across the click. Replaces the min-width pin from fix attempt
1, which enlarged buttons by up to 0.64px (ceil of fractional width) and
leaked the pin after restore.
Applies to paste-view Copy/Link (paste.html + paste.js copyFeedback) and
the /new result-box copy button (new.js). Verified with CDP bounding-box
probes: Copy width/x identical before/during/after at 1400x900 and
375x812 (including the previously failing 52.36px mobile case), Link
button static, checkmark visible during feedback, no minWidth pin set.
fen