feat: refactor to use gpui event instead of local state (#18)

Reviewed-on: #18
Co-authored-by: Ren Amamiya <reya@lume.nu>
Co-committed-by: Ren Amamiya <reya@lume.nu>

.agents/skills/gpui-test/SKILL.md

@@ -0,0 +1,94 @@
+---
+name: gpui-test
+description: Writing tests for GPUI applications. Use when testing components, async operations, or UI behavior.
+---
+
+## Overview
+
+GPUI provides a comprehensive testing framework that allows you to test UI components, async operations, and distributed systems. Tests run on a single-threaded executor that provides deterministic execution and the ability to test complex async scenarios. GPUI tests use the `#[gpui::test]` attribute and work with `TestAppContext` for basic testing and `VisualTestContext` for window-dependent tests.
+
+### Rules
+
+- If test does not require windows or rendering, we can avoid use `[gpui::test]` and `TestAppContext`, just write simple rust test.
+
+## Core Testing Infrastructure
+
+### Test Attributes
+
+#### Basic Test
+
+```rust
+#[gpui::test]
+fn my_test(cx: &mut TestAppContext) {
+    // Test implementation
+}
+```
+
+#### Async Test
+
+```rust
+#[gpui::test]
+async fn my_async_test(cx: &mut TestAppContext) {
+    // Async test implementation
+}
+```
+
+#### Property Test with Iterations
+
+```rust
+#[gpui::test(iterations = 10)]
+fn my_property_test(cx: &mut TestAppContext, mut rng: StdRng) {
+    // Property testing with random data
+}
+```
+
+### Test Contexts
+
+#### TestAppContext
+
+`TestAppContext` provides access to GPUI's core functionality without windows:
+
+```rust
+#[gpui::test]
+fn test_entity_operations(cx: &mut TestAppContext) {
+    // Create entities
+    let entity = cx.new(|cx| MyComponent::new(cx));
+
+    // Update entities
+    entity.update(cx, |component, cx| {
+        component.value = 42;
+        cx.notify();
+    });
+
+    // Read entities
+    let value = entity.read_with(cx, |component, _| component.value);
+    assert_eq!(value, 42);
+}
+```
+
+#### VisualTestContext
+
+`VisualTestContext` extends `TestAppContext` with window support:
+
+```rust
+#[gpui::test]
+fn test_with_window(cx: &mut TestAppContext) {
+    // Create window with component
+    let window = cx.update(|cx| {
+        cx.open_window(Default::default(), |_, cx| {
+            cx.new(|cx| MyComponent::new(cx))
+        }).unwrap()
+    });
+
+    // Convert to visual context
+    let mut cx = VisualTestContext::from_window(window.into(), cx);
+
+    // Access window and component
+    let component = window.root(&mut cx).unwrap();
+}
+```
+
+## Additional Resources
+
+- For detailed testing patterns and examples, see [reference.md](reference.md)
+- For best practices and running tests, see [examples.md](examples.md)