Add the Variable node and show the variable name in node titles

Get/Set variable nodes now title themselves "Get <name>" / "Set <name>", and
the new Variable node just "<name>"; the title is the same folded or open,
and a collapsed node shrinks to it. The redundant "Variable: <name>" row is
gone unless the variable was deleted ("<name>?" is the only hint then).

The Variable node sets its value when an exec flow arrives and exposes the
value at any time. Its output is read when a downstream node pulls it, not
frozen at the write, so count = count + 1 is one Variable node plus an Add.
Get variable keeps reading once per pulse: switching it would change the
behaviour of existing games.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tools/e2e/23-variable-nodes.mjs

@@ -35,7 +35,22 @@ const logicGraph = {
 };
 
 export async function variableNodes(t) {
-  const { check, sleep, evaluate, json, shot, click, locate, undo, entity, asset, mutate, stop } = t;
+  const {
+    check,
+    sleep,
+    evaluate,
+    json,
+    shot,
+    click,
+    locate,
+    undo,
+    entity,
+    asset,
+    mutate,
+    stop,
+    typeText,
+    press,
+  } = t;
   const portAt = (nodeId, key, isOutput) =>
     json(`__gm.graph.portAt(${JSON.stringify(nodeId)}, ${JSON.stringify(key)}, ${isOutput})`);
   const portsOf = async (nodeId) =>
@@ -216,6 +231,76 @@ export async function variableNodes(t) {
     JSON.stringify(helper),
   );
 
+  // 23i. The Variable node: picked from the palette, titled by the variable picked in the inspector,
+  //      and in the run `vz = vz + 1` once a frame – its own output feeding its input via Add.
+  const nodeIds = async () => (await asset('vp-logic')).graph.nodes.map((n) => n.id);
+  const idsBefore = await nodeIds();
+  const centre = await json('__gm.graph.center()');
+  // Below the Owner node; centre + (250, 250) would land on the Pack.
+  await click(centre.x - 250, centre.y + 250, 'right');
+  await sleep(150);
+  // Its description is the one that says "any time"; "variable" would put Get variable first.
+  await typeText('any time');
+  await sleep(200);
+  await press('Enter');
+  await sleep(300);
+  const added = (await asset('vp-logic')).graph.nodes.find((n) => !idsBefore.includes(n.id));
+  check('the palette offers the Variable node', added?.type === 'Variable', JSON.stringify(added));
+  const variableId = added?.id ?? '';
+  const titleOf = (id) => json(`__gm.graph.nodeLabel(${JSON.stringify(id)})`);
+  const untitled = await titleOf(variableId);
+  // The node's own title says "Variable" too, and the canvas is drawn first.
+  const picker = await json(`__gm.inspectorField('Variable', true)`);
+  await click(picker.x, picker.y);
+  await sleep(200);
+  await clickLast('vz');
+  await sleep(300);
+  check(
+    'picking its variable makes that the title, and drops the row that would repeat it',
+    untitled === 'Variable' &&
+      (await titleOf(variableId)) === 'vz' &&
+      (await json(`__gm.graph.nodeSettings(${JSON.stringify(variableId)})`)).length === 0,
+    JSON.stringify({ untitled, titled: await titleOf(variableId), picker }),
+  );
+  await shot('05-variable-node');
+
+  await mutate(`
+    const g = __gm.state.project.assets.find((x) => x.id === 'vp-logic').graph;
+    g.nodes.push(
+      ${JSON.stringify(node('vp-add', 'Add', 800, 200, { b: 1 }))},
+      ${JSON.stringify(node('vp-set-vx', 'SetVariable', 800, 400, { variable: 'vx' }))},
+      ${JSON.stringify(node('vp-set-gone', 'SetVariable', 800, 500, { variable: 'gone' }))},
+    );
+    g.edges.push(
+      ${JSON.stringify(edge('vp-e7', 'vp-move', 'exec', variableId, 'exec'))},
+      ${JSON.stringify(edge('vp-e8', variableId, 'value', 'vp-add', 'a'))},
+      ${JSON.stringify(edge('vp-e9', 'vp-add', 'result', variableId, 'value'))},
+    );
+  `);
+  await sleep(300);
+  const settingsOf = (id) => json(`__gm.graph.nodeSettings(${JSON.stringify(id)})`);
+  const named = { title: await titleOf('vp-set-vx'), rows: await settingsOf('vp-set-vx') };
+  const gone = { title: await titleOf('vp-set-gone'), rows: await settingsOf('vp-set-gone') };
+  check(
+    'Set variable names its variable too, and a deleted one keeps the row that marks it',
+    named.title === 'Set vx' &&
+      named.rows.length === 0 &&
+      gone.title === 'Set gone' &&
+      JSON.stringify(gone.rows) === '["Variable: gone?"]',
+    JSON.stringify({ named, gone }),
+  );
+
+  await t.play();
+  await sleep(1000);
+  const counted = (await entity('vp-brain'))?.props.vz;
+  await stop();
+  await sleep(300);
+  check(
+    'in the run it reads through its own output and writes the sum back, so vz climbs',
+    typeof counted === 'number' && counted > 20,
+    `vz = ${counted} after ~1 s`,
+  );
+
   await mutate(`
     const p = __gm.state.project;
     p.assets = p.assets.filter((a) => a.id !== 'vp-logic');