PageScene: ColorAction signals panel refresh on apply/revert

When the user undoes a color change while the Object Panel is open,
the THREE.js material reverts correctly but the panel's local React
`color` state stays at the redo value — the panel preview Button and
the color input value disagree with the actual scene material.

Root cause: the per-frame `getSelectedSum` check in renderSingleFrame
pushes a fresh `objectPanel` slice to Zustand whenever transforms
change, which re-fires the panel's useEffect and re-reads
userData.color. Color changes don't move the sum, so the push never
happens after a color undo/redo.

Fix: ColorAction.apply/revert now calls
`editor.selection.updateSelectedUI()` after the engine setColor.
That pushes a new currentSceneObject reference into Zustand, the
panel's [currentSceneObject] effect fires, and
`setColor(editorEngine?.selected?.userData.color)` reads the freshly
reverted value. Same pattern the lock/transform paths already use
for UI sync.

frontend/apps/artcraft/app/src/pages/PageScene/engine/editor/actions/ColorAction.ts

@@ -4,6 +4,13 @@ import type { UndoableAction } from "../HistoryManager";
 // Records a color change. apply() and revert() both call
 // activeScene.setColor — the engine handles material magic. The action
 // captures the uuid + before/after hex pair at construction time.
+//
+// Each replay also fires SelectionBridge.updateSelectedUI() so the
+// Object Panel re-reads userData.color and refreshes its preview.
+// Without this, undo correctly reverts the THREE.js material but
+// ControlPanelSceneObject's local React state stays at the redo
+// value (the per-frame getSelectedSum check that picks up transform
+// changes doesn't notice color changes).
 export class ColorAction implements UndoableAction {
   readonly label = "Color";
 
@@ -16,9 +23,11 @@ export class ColorAction implements UndoableAction {
 
   apply(): void {
     this.editor.activeScene.setColor(this.uuid, this.after);
+    this.editor.selection.updateSelectedUI();
   }
 
   revert(): void {
     this.editor.activeScene.setColor(this.uuid, this.before);
+    this.editor.selection.updateSelectedUI();
   }
 }