ci(testing): reduce e2e test parallelism in CI to fix flaky tests

Work around Stencil v4 e2e test parallelization issues that cause
random timeouts in CI but not locally. Changes only apply when CI=true.

- Add --disable-gpu browser arg in stencil.config.ts
- Add --max-workers=2 in run-tests.cjs

See: stenciljs/core#6157

Author: adrianschmidt

scripts/run-tests.cjs

@@ -25,6 +25,13 @@ const isDebug =
 
 const args = ['test', '--spec', '--e2e'];
 
+// Reduce parallelism in CI to work around Stencil v4 e2e test issues
+// See: https://github.com/stenciljs/core/issues/6157
+if (isCI) {
+    args.push('--max-workers=2');
+    console.log('CI detected, reducing parallelism with --max-workers=2');
+}
+
 // Add verbose flag if debug mode is enabled
 if (isDebug) {
     args.push('--verbose');

stencil.config.ts

@@ -53,7 +53,12 @@ export const config: Config = {
     tsconfig: './tsconfig.dev.json',
     globalStyle: 'src/global/core-styles.scss',
     testing: {
-        browserArgs: ['--enable-experimental-web-platform-features'],
+        browserArgs: [
+            '--enable-experimental-web-platform-features',
+            // Disable GPU in CI to work around Stencil v4 e2e test parallelization issues
+            // See: https://github.com/stenciljs/core/issues/6157
+            ...(process.env.CI ? ['--disable-gpu'] : []),
+        ],
         setupFilesAfterEnv: ['<rootDir>/src/test-setup.ts'],
         moduleNameMapper: {
             '^lodash-es$': 'lodash',