tui: add Approve component with y/n keybind

<Approve fileName oldText newText onDecision/> renders a unified diff
(+/-/space sigils, 4-col line numbers, add/del totals header) and
binds y -> accept, n/q/ESC -> reject via ink useInput.

Tests use ink-testing-library; each keystroke case awaits a microtask
flush before stdin.write so that ink's useEffect-installed 'readable'
listener has actually been attached at the moment the byte arrives.

src/tui/approve/Approve.tsx

@@ -0,0 +1,51 @@
+import React from 'react';
+import { Box, Text, useInput } from 'ink';
+import { computeHunks } from '../shared/diff.js';
+import { Hunk } from '../shared/types.js';
+
+export type Decision = 'accept' | 'reject';
+
+export interface ApproveProps {
+  fileName: string;
+  oldText: string;
+  newText: string;
+  onDecision: (d: Decision) => void;
+}
+
+export function Approve({ fileName, oldText, newText, onDecision }: ApproveProps): React.ReactElement {
+  const hunks = React.useMemo(() => computeHunks(oldText, newText), [oldText, newText]);
+  const adds = hunks.filter((h) => h.kind === 'add').length;
+  const dels = hunks.filter((h) => h.kind === 'del').length;
+
+  useInput((input, key) => {
+    if (input === 'y') return onDecision('accept');
+    if (input === 'n' || input === 'q' || key.escape) return onDecision('reject');
+  });
+
+  return (
+    <Box flexDirection="column">
+      <Text>
+        ─ Approve change? {fileName} ─── + {adds} lines, − {dels} lines ─
+      </Text>
+      <Box flexDirection="column">
+        {hunks.map((h, i) => (
+          <HunkLine key={i} hunk={h} />
+        ))}
+      </Box>
+      <Text>
+        y accept   n reject   q reject & quit   ESC reject
+      </Text>
+    </Box>
+  );
+}
+
+function HunkLine({ hunk }: { hunk: Hunk }): React.ReactElement {
+  const sigil = hunk.kind === 'add' ? '+' : hunk.kind === 'del' ? '-' : ' ';
+  const color = hunk.kind === 'add' ? 'green' : hunk.kind === 'del' ? 'red' : undefined;
+  const lineNoStr = String(hunk.lineNo).padStart(4, ' ');
+  return (
+    <Text color={color}>
+      {sigil} {lineNoStr}  {hunk.text}
+    </Text>
+  );
+}

tests/tui/Approve.test.tsx

@@ -0,0 +1,74 @@
+import React from 'react';
+import { describe, it, expect, vi } from 'vitest';
+import { render } from 'ink-testing-library';
+import { Approve } from '../../src/tui/approve/Approve.tsx';
+
+const OLD = 'PROGRAM PLC_PRG\nVAR\n  counter : INT := 0;\nEND_VAR';
+const NEW = 'PROGRAM PLC_PRG\nVAR\n  counter : DINT := 0;\n  overflow : BOOL;\nEND_VAR';
+
+describe('<Approve>', () => {
+  it('renders both deletions and additions in a unified diff', () => {
+    const { lastFrame } = render(
+      <Approve fileName="PLC_PRG.st" oldText={OLD} newText={NEW} onDecision={() => {}} />
+    );
+    const out = lastFrame()!;
+    expect(out).toContain('counter : INT := 0;');
+    expect(out).toContain('counter : DINT := 0;');
+    expect(out).toContain('overflow : BOOL;');
+    expect(out).toMatch(/Approve change\? PLC_PRG\.st/);
+  });
+
+  it('reports add/del totals in the header', () => {
+    const { lastFrame } = render(
+      <Approve fileName="x.st" oldText={OLD} newText={NEW} onDecision={() => {}} />
+    );
+    const out = lastFrame()!;
+    expect(out).toMatch(/\+ 2 lines.*− 1 lines/);
+  });
+
+  const flush = () => new Promise<void>((r) => setImmediate(r));
+
+  it('calls onDecision("accept") when y is pressed', async () => {
+    const decision = vi.fn();
+    const { stdin } = render(
+      <Approve fileName="x.st" oldText={OLD} newText={NEW} onDecision={decision} />
+    );
+    await flush();
+    stdin.write('y');
+    await flush();
+    expect(decision).toHaveBeenCalledWith('accept');
+  });
+
+  it('calls onDecision("reject") when n is pressed', async () => {
+    const decision = vi.fn();
+    const { stdin } = render(
+      <Approve fileName="x.st" oldText={OLD} newText={NEW} onDecision={decision} />
+    );
+    await flush();
+    stdin.write('n');
+    await flush();
+    expect(decision).toHaveBeenCalledWith('reject');
+  });
+
+  it('calls onDecision("reject") when q is pressed', async () => {
+    const decision = vi.fn();
+    const { stdin } = render(
+      <Approve fileName="x.st" oldText={OLD} newText={NEW} onDecision={decision} />
+    );
+    await flush();
+    stdin.write('q');
+    await flush();
+    expect(decision).toHaveBeenCalledWith('reject');
+  });
+
+  it('calls onDecision("reject") on escape', async () => {
+    const decision = vi.fn();
+    const { stdin } = render(
+      <Approve fileName="x.st" oldText={OLD} newText={NEW} onDecision={decision} />
+    );
+    await flush();
+    stdin.write(String.fromCharCode(27));
+    await flush();
+    expect(decision).toHaveBeenCalledWith('reject');
+  });
+});