test(tiles): the grid harness finds a tile's element, and serves the pure helpers

Five tile-grid tests defined the same `tileEl(id)` lookup and three more
inlined it; the harness (test/mocks/tile-grid-vm.ts) now exports it and
they import it. tile-grid-open-set built a second vm context just to read
constants.js, although the harness it already imports has loaded the same
file: it reads windowStub.CodemanTileGrid instead.

No assertion changed. Mutation-checked: tiles without their
data-session-id fail 34 tests across the seven files, and a broken
tileGridOpenSet fails the open-set cases.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

test/mocks/tile-grid-vm.ts

@@ -159,6 +159,8 @@ export const section = new FakeEl();
 section.id = 'tileGrid';
 section.className = 'tile-grid';
 main.appendChild(section);
+/** The grid's element for one tiled session (its `.tile`), found by its data-session-id. */
+export const tileEl = (id: string) => section.children.find((el) => el.dataset.sessionId === id) as FakeEl;
 
 /** Extra elements `document.querySelector` finds, by exact selector (e.g. '.btn-split'). */
 export const bySelector = new Map<string, FakeEl>();

test/tile-grid-attach.test.ts

@@ -18,18 +18,16 @@
  */
 import { beforeEach, describe, expect, it, vi } from 'vitest';
 import {
-  FakeEl,
   FakeTile,
   fetchSpy,
   makeGridApp,
   resetGridHarness,
-  section,
   windowStub,
   type GridApp,
+  tileEl,
 } from './mocks/tile-grid-vm.js';
 
 const IDS = ['s-a', 's-b', 's-c'];
-const tileEl = (id: string) => section.children.find((el) => el.dataset.sessionId === id) as FakeEl;
 const overlayOf = (id: string) => tileEl(id).children[1].children.find((c) => c.className === 'tile-attach') ?? null;
 const visible = (id: string) => !!overlayOf(id) && !overlayOf(id)!.hidden;
 const textOf = (id: string) => overlayOf(id)!.children[0].textContent;

test/tile-grid-auto-join.test.ts

@@ -18,7 +18,7 @@
 import { readFileSync } from 'node:fs';
 import { resolve } from 'node:path';
 import { beforeEach, describe, expect, it, vi } from 'vitest';
-import { FakeEl, FakeTile, makeGridApp, resetGridHarness, section, type GridApp } from './mocks/tile-grid-vm.js';
+import { FakeTile, makeGridApp, resetGridHarness, section, type GridApp, tileEl } from './mocks/tile-grid-vm.js';
 
 const IDS = ['s-a', 's-b'];
 const addSession = (app: GridApp, id: string, workingDir = '/w') =>
@@ -52,7 +52,7 @@ describe('Run from this tab', () => {
     app.openTileGrid(IDS);
     addSession(app, 's-new');
     app._joinTileGridFromRun('s-new');
-    const tile = section.children.find((el) => el.dataset.sessionId === 's-new') as FakeEl;
+    const tile = tileEl('s-new');
     const overlay = tile.children[1].children.find((c) => c.className === 'tile-attach');
     expect(!overlay || overlay.hidden).toBe(true);
   });

test/tile-grid-chrome.test.ts

@@ -18,7 +18,7 @@
 import { readFileSync } from 'node:fs';
 import { resolve } from 'node:path';
 import { beforeEach, describe, expect, it, vi } from 'vitest';
-import { FakeEl, FakeTile, makeGridApp, resetGridHarness, section, type GridApp } from './mocks/tile-grid-vm.js';
+import { FakeEl, FakeTile, makeGridApp, resetGridHarness, type GridApp, tileEl } from './mocks/tile-grid-vm.js';
 
 const IDS = ['s-a', 's-b', 's-c'];
 
@@ -38,7 +38,6 @@ function openGrid(): GridApp {
   return app;
 }
 
-const tileEl = (id: string) => section.children.find((el) => el.dataset.sessionId === id) as FakeEl;
 const headerOf = (id: string) => tileEl(id).children[0];
 const buttonOf = (id: string, cls: string) =>
   headerOf(id).children[2].children.find((b) => b.className.includes(cls)) as FakeEl;
@@ -99,7 +98,7 @@ describe('the header', () => {
 describe('header buttons', () => {
   it('are ⋯ ⤢ × and nothing else: no + (owner decision 9)', () => {
     const app = openGrid();
-    const tile = section.children.find((el) => el.dataset.sessionId === 's-a') as FakeEl;
+    const tile = tileEl('s-a');
     const actions = tile.children[0].children.find((c) => c.className === 'tile-actions') as FakeEl;
     expect(actions.children.map((b) => b.className)).toEqual([
       'tile-btn tile-menu',

test/tile-grid-dividers.test.ts

@@ -22,10 +22,10 @@ import {
   resetGridHarness,
   section,
   type GridApp,
+  tileEl,
 } from './mocks/tile-grid-vm.js';
 
 const SIX = ['s-a', 's-b', 's-c', 's-d', 's-e', 's-f'];
-const tileEl = (id: string) => section.children.find((el) => el.dataset.sessionId === id) as FakeEl;
 const divider = (app: GridApp, key: string) => app._tileGrid.dividers.get(key) as FakeEl;
 const tile = (id: string) => FakeTile.all.find((t) => t.sessionId === id) as FakeTile;
 

test/tile-grid-entry-points.test.ts

@@ -24,10 +24,10 @@ import {
   section,
   windowStub,
   type GridApp,
+  tileEl,
 } from './mocks/tile-grid-vm.js';
 
 const IDS = ['s-a', 's-b', 's-c'];
-const tileEl = (id: string) => section.children.find((el) => el.dataset.sessionId === id) as FakeEl;
 const slots = () => section.children.filter((el) => el.className === 'tile-slot');
 const dragEvent = () => ({ preventDefault: vi.fn(), stopPropagation: vi.fn(), dataTransfer: { dropEffect: '' } });
 

test/tile-grid-open-set.test.ts

@@ -11,12 +11,11 @@
  *   (`toggleTileGrid`); right-click (contextmenu) opens the picker. With the
  *   grid open the picker shows the current tiles, and Open replaces them.
  *
- * Pure helper via `vm`, the app via the shared harness (test/mocks/tile-grid-vm.ts).
+ * The pure helper and the app both via the shared harness (test/mocks/tile-grid-vm.ts).
  * Port: N/A.
  */
 import { readFileSync } from 'node:fs';
 import { resolve } from 'node:path';
-import vm from 'node:vm';
 import { beforeEach, describe, expect, it, vi } from 'vitest';
 import {
   FakeEl,
@@ -25,17 +24,14 @@ import {
   documentAddEventListener,
   makeGridApp,
   resetGridHarness,
+  windowStub,
 } from './mocks/tile-grid-vm.js';
 
 type OpenSet = { source: string; ids: string[]; focusedId: string | null } | null;
 type Helpers = { tileGridOpenSet(p: Record<string, unknown>): OpenSet; TILE_GRID_MAX: number };
 
-function loadHelpers(): Helpers {
-  const context = vm.createContext({ window: {}, globalThis: {} });
-  vm.runInContext(readFileSync(resolve(import.meta.dirname, '../src/web/public/constants.js'), 'utf8'), context);
-  return (context.window as { CodemanTileGrid: Helpers }).CodemanTileGrid;
-}
-const T = loadHelpers();
+// constants.js as the harness loaded it (window.CodemanTileGrid).
+const T = windowStub.CodemanTileGrid as Helpers;
 const INDEX_HTML = readFileSync(resolve(import.meta.dirname, '../src/web/public/index.html'), 'utf8');
 
 const order = Array.from({ length: 9 }, (_, i) => `t${i + 1}`);

test/tile-grid-select-branch.test.ts

@@ -26,8 +26,8 @@ import {
   localStore,
   makeGridApp,
   resetGridHarness,
-  section,
   type GridApp,
+  tileEl,
 } from './mocks/tile-grid-vm.js';
 
 const IDS = ['s-a', 's-b', 's-c'];
@@ -163,7 +163,7 @@ describe('moving focus between tiles', () => {
   it('pressing a tile is a human selection of its session', async () => {
     const app = openGrid();
     app.selectSession = vi.fn();
-    const tileB = section.children.find((el) => el.dataset.sessionId === 's-b');
+    const tileB = tileEl('s-b');
     tileB?.dispatch('pointerdown');
     expect(app.selectSession).toHaveBeenCalledWith('s-b');
   });

test/tile-grid-zoom.test.ts

@@ -16,10 +16,17 @@
 import { readFileSync } from 'node:fs';
 import { resolve } from 'node:path';
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
-import { FakeEl, FakeTile, makeGridApp, resetGridHarness, section, type GridApp } from './mocks/tile-grid-vm.js';
+import {
+  FakeEl,
+  FakeTile,
+  makeGridApp,
+  resetGridHarness,
+  section,
+  type GridApp,
+  tileEl,
+} from './mocks/tile-grid-vm.js';
 
 const IDS = ['s-a', 's-b', 's-c', 's-d'];
-const tileEl = (id: string) => section.children.find((el) => el.dataset.sessionId === id) as FakeEl;
 const zoomButton = (id: string) =>
   tileEl(id).children[0].children[2].children.find((b) => b.className.includes('tile-zoom')) as FakeEl;