Convert to unlit rendering and fix connection update error

Lighting changes:
- Disabled HemisphericLight in customEnvironment
- Changed all materials from diffuse to emissive colors
- Added disableLighting=true to all StandardMaterials
- Updated toolbox colors, diagram entities, and spinner

Bug fix:
- Fixed "Cannot read properties of undefined (reading 'pickedMesh')" error
- Added defensive check in DiagramObject.updateConnection()
- Now validates hit array has at least 2 elements before accessing

Materials now render at full brightness with unlit/flat shading.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/diagram/diagramObject.ts

@@ -323,6 +323,9 @@ export class DiagramObject {
                 return false;
             }
         });
+        if (!hit || hit.length < 2) {
+            return; // No valid intersection found, skip update
+        }
         if (hit[0].pickedMesh.id === this._to) {
             hit.reverse();
         }

src/diagram/functions/buildMeshFromDiagramEntity.ts

@@ -192,7 +192,9 @@ export function buildMissingMaterial(name: string, scene: Scene, color: string):
     }
     const newMaterial = new StandardMaterial(name, scene);
     newMaterial.id = name;
-    newMaterial.diffuseColor = Color3.FromHexString(color);
+    newMaterial.emissiveColor = Color3.FromHexString(color);
+    newMaterial.disableLighting = true;
+    // newMaterial.diffuseColor = Color3.FromHexString(color);
     newMaterial.alpha = 1;
     return newMaterial;
 }

src/objects/spinner.ts

@@ -53,8 +53,11 @@ export class Spinner {
         const text = new DynamicTexture("spinner", {width: 1024, height: 1024}, this._scene, false);
         text.drawText("Please Wait", 250, 500, "bold 150px Segoe UI", "white", "transparent", true, true);
         spinner.rotation.z = Math.PI;
-        material.diffuseTexture = text;
-        material.diffuseColor.set(.5, .5, 0);
+        material.emissiveTexture = text;
+        material.emissiveColor.set(.5, .5, 0);
+        material.disableLighting = true;
+        // material.diffuseTexture = text;
+        // material.diffuseColor.set(.5, .5, 0);
         const rotate = new Animation("rotate", "rotation.y", 10,
             Animation.ANIMATIONTYPE_FLOAT, Animation.ANIMATIONLOOPMODE_CYCLE);
         const keys = [];

src/toolbox/functions/buildColor.ts

@@ -16,8 +16,11 @@ export async function buildColor(color: Color3, scene: Scene, parent: TransformN
     const width = .1;
     const height = .1;
     const material = new StandardMaterial("material-" + color.toHexString(), scene);
+    material.emissiveColor = color;
     material.diffuseColor = color;
-    material.ambientColor = color;
+    material.disableLighting = true;
+    // material.diffuseColor = color;
+    // material.ambientColor = color;
     //material.roughness = 1;
     material.specularPower = 64;
     //     material.ambientColor = color;

src/util/customEnvironment.ts

@@ -33,10 +33,11 @@ export class CustomEnvironment {
         this.name = name;
 
         this.scene.ambientColor = new Color3(.1, .1, .1);
-        const light = new HemisphericLight("light1", new Vector3(.5, 1, 1).normalize(), this.scene);
-        light.groundColor = new Color3(0, 0, 0);
-        light.diffuse = new Color3(1, 1, 1);
-        light.intensity = .8;
+        // Light disabled for unlit rendering
+        // const light = new HemisphericLight("light1", new Vector3(.5, 1, 1).normalize(), this.scene);
+        // light.groundColor = new Color3(0, 0, 0);
+        // light.diffuse = new Color3(1, 1, 1);
+        // light.intensity = .8;
         const physics = new CustomPhysics(this.scene);
         physics
             .initializeAsync()