Introduces UiButton: a dedicated dat-widget button that ports UIElement_Button
(RegisterElementClass(1,...) @ acclient_2013_pseudo_c.txt:125828). State selection,
tiled DrawSprite, and label rendering mirror UiDatElement exactly so the chat Send
and Max/Min buttons have zero behavioral change.
DatWidgetFactory now maps Type 1 → UiButton (beside Type 7 → UiMeter, Type 11 →
UiScrollbar). ChatWindowController's Send and Max/Min bind blocks updated from
UiDatElement casts to UiButton casts; ClickThrough=false lines dropped (UiButton
is interactive by construction).
The old UiPanel.cs UiButton (a plain dev-scaffold rect+text button with no dat
sprites) is renamed UiSimpleButton to free the name — no production code
instantiated it.
Full suite: 402 passed, 2 skipped, 0 failed.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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