fix(tui): Trigger initial render when start() is called

The demos were not showing any output until user input because:
- Components were added before ui.start() was called
- addChild calls requestRender() but it returns early if \!isStarted
- So no initial render happened until user input triggered one

Now ui.start() triggers an initial render if components exist.

packages/tui/src/tui.ts

@@ -238,6 +238,11 @@ export class TUI extends Container {
 		} catch (error) {
 			console.error("Error starting terminal:", error);
 		}
+
+		// Trigger initial render if we have components
+		if (this.children.length > 0) {
+			this.requestRender();
+		}
 	}
 
 	stop(): void {