fix(app): restore the native terminal cursor beside the prompt

Measure the font sample outside the grid whose width is derived from those metrics. On cold Android startup the one-column grid wrapped the sample, temporarily shrinking the emulator and clamping the restored cursor before the final layout.

packages/app/src/terminal/native-renderer/terminal-grid-view.browser.test.tsx

@@ -0,0 +1,54 @@
+import React, { act } from "react";
+import { createRoot } from "react-dom/client";
+import { expect, test } from "vitest";
+import { TerminalGridView } from "./terminal-grid-view.native";
+import type { TerminalViewportState } from "./headless-terminal-state";
+import type { TerminalGridCellMetrics } from "./terminal-grid-metrics";
+
+test("measures a single font cell before the terminal has its viewport columns", async () => {
+  const container = document.createElement("div");
+  container.style.cssText = "width: 400px; height: 700px; display: flex";
+  document.body.appendChild(container);
+  const root = createRoot(container);
+  const measurements: TerminalGridCellMetrics[] = [];
+  const state: TerminalViewportState = {
+    rows: 1,
+    cols: 1,
+    firstRow: 0,
+    oldestRow: 0,
+    newestRow: 0,
+    grid: [[{ char: " " }]],
+    cursor: { row: 0, col: 0 },
+  };
+  const style = { flex: 1 };
+  const recordMeasurement = (metrics: TerminalGridCellMetrics) => measurements.push(metrics);
+  try {
+    act(() =>
+      root.render(
+        React.createElement(TerminalGridView, {
+          state,
+          fontSize: 12,
+          style,
+          onCellMetricsChange: recordMeasurement,
+        }),
+      ),
+    );
+    await expect.poll(() => measurements.length).toBeGreaterThan(0);
+    const sample = [...container.querySelectorAll("div")].find(
+      (element) => element.textContent === "mmmmmmmmmm" && element.childElementCount === 0,
+    );
+    expect(sample).toBeDefined();
+    // Native Text wraps to its containing block. Font measurement must fit even
+    // when the terminal starts with one column, before layout determines its size.
+    expect(sample!.parentElement!.getBoundingClientRect().width).toBeGreaterThanOrEqual(
+      sample!.getBoundingClientRect().width,
+    );
+    // The first measurement is used to size the emulator before restore data arrives.
+    // A wrapped ten-character sample reports a fraction of a cell and multiple lines.
+    expect(measurements[0].cellWidth).toBeGreaterThan(5);
+    expect(measurements[0].cellHeight).toBeLessThan(24);
+  } finally {
+    act(() => root.unmount());
+    container.remove();
+  }
+});

packages/app/src/terminal/native-renderer/terminal-grid-view.native.tsx

@@ -407,10 +407,11 @@ export function TerminalGridView({
 
   return (
     <View onLayout={handleContainerLayout} pointerEvents="none" style={containerStyle}>
+      {/* Measure against the viewport, independently of the grid width derived from these metrics. */}
+      <Text onLayout={handleMeasure} pointerEvents="none" style={measureStyle}>
+        {MEASURE_TEXT}
+      </Text>
       <View style={gridStyle}>
-        <Text onLayout={handleMeasure} pointerEvents="none" style={measureStyle}>
-          {MEASURE_TEXT}
-        </Text>
         {rows.map((row) => (
           <MemoTerminalGridRow
             key={row.index}