chore(example): revamp Button example as an interactive playground

Replace the long exhaustive grid with a compact playground: a live Button
driven by Chip controls (mode/size/shape/icon-position) and Switch rows
(show icon/disabled/loading/selected/compact), with smart gating so a control
is never a no-op (icon-position only with an icon; compact only when size is
unset). Keeps trimmed showcase sections: Modes, States, Size, Shape, Toggle,
Custom.

Author: azizbecha