test: add sample Slint file and test results template

Add test files for manual verification of the Slint LSP integration:
- hello.slint: Sample Slint component with common UI elements
- TEST_RESULTS.md: Checklist template for testing LSP features

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

test-files/hello.slint

@@ -0,0 +1,22 @@
+import { Button, VerticalBox } from "std-widgets.slint";
+
+export component HelloWorld inherits Window {
+    width: 400px;
+    height: 300px;
+
+    VerticalBox {
+        alignment: center;
+
+        Text {
+            text: "Hello, World!";
+            font-size: 24px;
+        }
+
+        Button {
+            text: "Click me";
+            clicked => {
+                debug("Button clicked!");
+            }
+        }
+    }
+}