feat(app): collapse workspace header button labels on narrow rows

Measure the header row width and hide text labels on the Open,
Scripts, and git action split buttons below 700px so the header
fits without wrapping on split-pane layouts.

packages/app/src/hooks/use-container-width.ts

@@ -0,0 +1,18 @@
+import { useCallback, useState } from "react";
+import type { LayoutChangeEvent } from "react-native";
+
+/**
+ * Tracks the width of a container via onLayout.
+ */
+export function useContainerWidth(): {
+  onLayout: (e: LayoutChangeEvent) => void;
+  width: number;
+} {
+  const [width, setWidth] = useState(0);
+  return {
+    onLayout: useCallback((e: LayoutChangeEvent) => {
+      setWidth(e.nativeEvent.layout.width);
+    }, []),
+    width,
+  };
+}