feat: extend copilot instruction for meshEntity refs

Author: nroi

.github/.copilot-instructions.md

@@ -83,6 +83,38 @@ Resources use consistent schema structures:
 - `spec` - Object specification (user-defined configuration)
 - `status` - Object status (system-managed state)
 
+### meshEntity Reference Pattern
+When referring to other meshEntities (like `project_role_ref` in landingzone resources), implement them with this pattern:
+- **User provides**: Only the `name` attribute (required)
+- **System sets**: The `kind` attribute automatically (computed with default value)
+
+Example implementation:
+```go
+schema.SingleNestedAttribute{
+    MarkdownDescription: "the meshProject role",
+    Required:            true,
+    Attributes: map[string]schema.Attribute{
+        "name": schema.StringAttribute{
+            Required:            true,
+            MarkdownDescription: "The identifier of the meshProjectRole",
+        },
+        "kind": schema.StringAttribute{
+            MarkdownDescription: "meshObject type, always `meshProjectRole`.",
+            Computed:            true,
+            Default:             stringdefault.StaticString("meshProjectRole"),
+            Validators: []validator.String{
+                stringvalidator.OneOf([]string{"meshProjectRole"}...),
+            },
+            PlanModifiers: []planmodifier.String{stringplanmodifier.UseStateForUnknown()},
+        },
+    },
+}
+```
+
+This pattern ensures:
+- Simplified user experience (only need to specify the name)
+- Consistent reference structure across all meshEntity references
+
 ## Common Development Tasks
 
 ### Adding a New Resource