fix: prevent UI from going blank when terminal panel is opened on macOS

- Changed ChatView from fixed positioning to absolute positioning
- Added proper height and positioning styles to body and #root elements
- Ensures webview content stays within container boundaries when terminal panel resizes the viewport

Fixes #9227

webview-ui/src/components/chat/ChatView.tsx

@@ -1355,9 +1355,7 @@ const ChatViewComponent: React.ForwardRefRenderFunction<ChatViewRef, ChatViewPro
 	const areButtonsVisible = showScrollToBottom || primaryButtonText || secondaryButtonText || isStreaming
 
 	return (
-		<div
-			data-testid="chat-view"
-			className={isHidden ? "hidden" : "fixed top-0 left-0 right-0 bottom-0 flex flex-col overflow-hidden"}>
+		<div data-testid="chat-view" className={isHidden ? "hidden" : "absolute inset-0 flex flex-col overflow-hidden"}>
 			{telemetrySetting === "unset" && <TelemetryBanner />}
 			{(showAnnouncement || showAnnouncementModal) && (
 				<Announcement

webview-ui/src/index.css

@@ -231,6 +231,14 @@ html {
 body {
 	margin: 0;
 	line-height: 1.25;
+	height: 100%;
+	position: relative;
+	overflow: hidden;
+}
+
+#root {
+	height: 100%;
+	position: relative;
 }
 
 body.scrollable,