docs(playwright): clarify why SQL Lab needs a separate project config

Explain that /tabstateview/* server-side state per user forces sequential
execution, unlike dataset/dashboard/chart tests that use isolated resources.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: sadpandajoe

superset-frontend/playwright.config.ts

@@ -105,10 +105,12 @@ export default defineConfig({
       },
     },
     {
-      // SQL Lab tests share backend tab state per user (/tabstateview/*).
-      // fullyParallel: false ensures all tests run sequentially on one worker
-      // without the skip-on-failure behavior of serial mode — a single test
-      // failure still reports remaining tests independently.
+      // SQL Lab needs its own project because tab state is stored server-side
+      // per user (/tabstateview/*). All workers share the same auth user, so
+      // parallel workers mutating tabs would cause nondeterministic tab counts
+      // and cross-worker tab deletions. Other test suites (dataset, dashboard,
+      // chart) don't need this because they create/delete isolated resources
+      // via API with unique names — no shared mutable state between tests.
       name: 'chromium-sqllab',
       testMatch: '**/tests/sqllab/**/*.spec.ts',
       fullyParallel: false,

superset-frontend/playwright/tests/sqllab/sqllab.spec.ts

@@ -18,14 +18,12 @@
  */
 
 /**
- * SQL Lab E2E tests — sequential via project-level fullyParallel: false.
+ * SQL Lab E2E tests — sequential via chromium-sqllab project.
  *
- * SQL Lab persists tabs per user via /tabstateview/*. With fullyParallel and
- * multiple workers, tests sharing the same authenticated user can overwrite
- * each other's tab/query state, making tab-count and reload assertions
- * nondeterministic. The chromium-sqllab project in playwright.config.ts
- * sets fullyParallel: false so all tests in this file run sequentially on
- * one worker — without the skip-on-failure behavior of serial mode.
+ * Tab state is stored server-side per user (/tabstateview/*), and all workers
+ * share the same authenticated user. Parallel workers adding/removing tabs
+ * would cause nondeterministic tab counts and cross-worker deletions.
+ * See playwright.config.ts chromium-sqllab project for details.
  */
 
 import { test, expect } from '../../helpers/fixtures/testAssets';