Fix double node creation when picking a palette entry by click

- TextField: new onSubmit callback (Enter only, independent of value change)
- NodePalette: use onSubmit instead of onChange, add per-open picked guard
- e2e: new check 13a (type + click row -> exactly one node), wait for
  Chromium exit in finally with SIGKILL escalation after 5s

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

tools/e2e.mjs

@@ -362,8 +362,28 @@ try {
   const mulUndone = await nodeOf('n-mul');
   check('undo moves the node back', mulUndone.x === mulBefore.x && mulUndone.y === mulBefore.y, `${mulUndone.x},${mulUndone.y}`);
 
-  // 13b. Right-click the empty canvas → palette → search "log" → Enter adds a Log node.
+  // 13a. Regression: typing a query and then *clicking* a row must add exactly one node.
+  // (Previously the search field's blur-commit picked the first match and the row click
+  // picked it again → two nodes.)
   const gcenter = JSON.parse(await evaluate(`JSON.stringify(__gm.graph.center())`));
+  const beforeClickPick = await graphCounts();
+  await click(gcenter.x + 250, gcenter.y + 250, 'right');
+  await sleep(250);
+  check('node palette opens (row-click case)', Boolean(await evaluate(`__gm.locate('Search nodes…')`)));
+  await typeText('stop');
+  await sleep(150);
+  const stopRow = await locate('Stop game'); // unique on screen (nothing else on screen shows this label)
+  await click(stopRow.x, stopRow.y);
+  await sleep(250);
+  const afterClickPick = await graphCounts();
+  check('clicking a palette row adds exactly one node', afterClickPick.nodes === beforeClickPick.nodes + 1, JSON.stringify({ beforeClickPick, afterClickPick }));
+  check('palette closed after row click', !(await evaluate(`__gm.locate('Search nodes…')`)));
+  // Undo so 13b finds the same empty spot and the expected graph.
+  await keyPress('z', 'KeyZ', { modifiers: 2, windowsVirtualKeyCode: 90 });
+  await sleep(150);
+  check('undo removes the clicked node again', (await graphCounts()).nodes === beforeClickPick.nodes);
+
+  // 13b. Right-click the empty canvas → palette → search "log" → Enter adds a Log node.
   const before13 = await graphCounts();
   await click(gcenter.x + 250, gcenter.y + 250, 'right');
   await sleep(250);
@@ -433,7 +453,14 @@ try {
   console.error(error);
   failures++;
 } finally {
-  chrome.kill('SIGTERM');
+  // Wait for chromium to actually exit (a SwiftShader GPU process kept rendering at full CPU
+  // once when only SIGTERM was sent); escalate to SIGKILL if it does not stop in time.
+  await new Promise((resolve) => {
+    if (chrome.exitCode !== null) return resolve();
+    const timer = setTimeout(() => { chrome.kill('SIGKILL'); }, 5000);
+    chrome.once('exit', () => { clearTimeout(timer); resolve(); });
+    chrome.kill('SIGTERM');
+  });
 }
 if (consoleLog.length) console.log('--- console ---\n' + consoleLog.slice(0, 20).join('\n'));
 process.exit(failures ? 1 : 0);