Sync HUD and enable all paint channels on pipette pick

After a successful pipette pick the painter now enables all four paint
channels (albedo, metallic/smoothness, occlusion, emission) and raises a
Picked event. The HUD subscribes and re-syncs every widget (toggles,
sliders, both colour pickers) to the adopted brush values.

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

Assets/Scripts/MeshPainter.Pick.cs

@@ -1,3 +1,4 @@
+using System;
 using UnityEngine;
 
 public partial class MeshPainter
@@ -18,6 +19,12 @@ public partial class MeshPainter
              "(all alphas set to 1) instead of painting. Held button picks only once.")]
     public bool pipette = false;
 
+    /// <summary>
+    /// Raised after a successful pick, once the brush has adopted the sampled values and all four
+    /// paint-channel flags have been enabled. The in-game HUD listens to re-sync its widgets.
+    /// </summary>
+    public event Action Picked;
+
     private bool _pickHeld; // edge tracking so a held button picks once, not every frame
 
     /// <summary>
@@ -67,5 +74,14 @@ public partial class MeshPainter
         // "Set all alpha values to 1": full-strength adoption across every opacity control.
         metallicSmoothnessOpacity = 1f;
         occlusionOpacity = 1f;
+
+        // Picking a whole material implies repainting all of it, so enable every channel.
+        paintAlbedo = true;
+        paintMetallicSmoothness = true;
+        paintOcclusion = true;
+        paintEmission = true;
+
+        // Let listeners (the in-game HUD) refresh their widgets to the adopted values + flags.
+        Picked?.Invoke();
     }
 }