feat(migrate): ensureSpace helper

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/migrate/spaces.test.js

@@ -0,0 +1,14 @@
+import { describe, it, expect, beforeAll } from 'vitest';
+import { resetDb } from '../helpers/db.js';
+import { migrateUp } from '../../lib/db/migrate.js';
+import { ensureSpace } from '../../migrate/spaces.js';
+
+beforeAll(async () => { await resetDb(); await migrateUp(); });
+
+describe('ensureSpace', () => {
+  it('creates a space once and reuses it by slug', async () => {
+    const a = await ensureSpace('void1', 'Void 1');
+    const b = await ensureSpace('void1', 'Void 1');
+    expect(a).toBe(b);
+  });
+});