Add Shift brush controls to paint mode

Hold Shift to momentarily enable the pipette (restores prior state on
release) and Shift+Scroll to resize the brush. The orbit zoom ignores the
wheel while Shift is held so it does not zoom and resize at once. The HUD
brush-size slider follows live via a BrushSizeChanged event, and the brush
preview now stays visible while Shift is held (drawn before the pipette
early-return) so the new size is visible while scrubbing.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Assets/Scripts/PaintHud.cs

@@ -148,13 +148,19 @@ public partial class PaintHud : MonoBehaviour
     {
         if (!newPainter || newPainter == painter || !_panel) return;
 
-        if (painter) painter.Picked -= SyncFromPainter;
+        if (painter)
+        {
+            painter.Picked -= SyncFromPainter;
+            painter.BrushSizeChanged -= SyncBrushSize;
+        }
         painter = newPainter;
 
         WirePanel(_panel.transform);
 
         // Re-sync every widget when the pipette adopts a sampled material (painter -> HUD).
         painter.Picked += SyncFromPainter;
+        // Re-sync the brush-size slider when Shift+wheel resizes the brush in-world (painter -> HUD).
+        painter.BrushSizeChanged += SyncBrushSize;
 
         // First bind this session: restore panel positions + brush values from disk (cross-session).
         // A later bind is an avatar respawn (scene switch) -> carry the in-session brush values onto the
@@ -169,7 +175,11 @@ public partial class PaintHud : MonoBehaviour
 
     private void OnDestroy()
     {
-        if (painter) painter.Picked -= SyncFromPainter;
+        if (painter)
+        {
+            painter.Picked -= SyncFromPainter;
+            painter.BrushSizeChanged -= SyncBrushSize;
+        }
     }
 
     private void OnModeChanged(GameMode mode)
@@ -309,6 +319,17 @@ public partial class PaintHud : MonoBehaviour
         RefreshMaskHighlights();
     }
 
+    /// <summary>
+    /// Pushes only the brush size back into its slider (painter -> HUD), e.g. after Shift+wheel
+    /// resized the brush in-world. The slider clamps to its own range and its listener writes the
+    /// clamped value back to the painter, so the wheel and the slider stay in agreement.
+    /// </summary>
+    private void SyncBrushSize()
+    {
+        if (!_panel || !painter) return;
+        SetSlider(_panel.transform, SliderBrushSize, painter.brushSize);
+    }
+
     private static void SetToggle(Transform panel, string name, bool value)
     {
         var toggle = Find<Toggle>(panel, name);