[Discover][Metrics] Fix flaky fullscreen interaction Scout test (elastic#270775)

## Summary

Fixes the flaky `fullscreen.spec.ts` Scout test ("should interact with
metrics in fullscreen mode").

**Two failure modes were identified:**

1. **Chrome header interception** (~65 failures, Apr 3–18): Already
fixed by PR elastic#264932 which added `chromeHeader.waitFor({ state: 'hidden'
})` to `toggleFullscreen()`. No recurrence since.

2. **`viewDetails` action not found** (2 failures, May 20): After
`clearSearch()`, the grid re-renders with the full unfiltered metric
set. The test immediately opened the context menu without waiting for
the grid to settle — the Lens embeddable hadn't finished re-mounting and
registering its actions.

**Fix:** Add `await
expect(metricsExperience.pagination.container).toBeVisible()` after
`clearSearch()` to wait for the grid to finish re-rendering before
opening the context menu. This matches the pattern used in
`grid.navigation.spec.ts`.

Closes elastic#261199

## Test plan

- [ ] Run `node scripts/scout run-tests --arch stateful --domain classic
--testFiles
src/platform/plugins/shared/discover/test/scout/ui/parallel_tests/metrics_experience/fullscreen.spec.ts`
locally
- [ ] Verify CI passes on stateful and serverless targets

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

Author: 3 people

src/dev/run_check.test.ts

@@ -66,6 +66,7 @@ jest.mock('@kbn/test', () => ({
 jest.mock('fs', () => ({
   ...jest.requireActual('fs'),
   existsSync: jest.fn(),
+  readdirSync: jest.fn(),
 }));
 
 const mockExecaFn = jest.fn();
@@ -81,6 +82,7 @@ const mockExecuteTypeCheckValidation = jest.requireMock('./type_check_validation
 const mockExecuteEslintValidation = jest.requireMock('./eslint/run_eslint_contract')
   .executeEslintValidation as jest.Mock;
 const mockExistsSync = jest.requireMock('fs').existsSync as jest.Mock;
+const mockReaddirSync = jest.requireMock('fs').readdirSync as jest.Mock;
 const mockExeca = mockExecaFn;
 
 let handler: (args: {
@@ -148,6 +150,7 @@ describe('run_check', () => {
       (p: string) =>
         p === '/repo/packages/foo/jest.config.js' || p === '/repo/packages/bar/jest.config.js'
     );
+    mockReaddirSync.mockReturnValue([]);
     mockExecuteEslintValidation.mockResolvedValue({
       fileCount: 3,
       fixedFiles: [],
@@ -289,10 +292,35 @@ describe('run_check', () => {
       },
     });
 
-    mockExistsSync.mockImplementation(
-      (p: string) =>
-        p ===
-        '/repo/x-pack/platform/plugins/shared/saved_objects_tagging/test/scout/api/playwright.config.ts'
+    mockExistsSync.mockReturnValue(false);
+    mockReaddirSync.mockImplementation((dir: string) =>
+      dir === '/repo/x-pack/platform/plugins/shared/saved_objects_tagging/test/scout/api'
+        ? ['playwright.config.ts']
+        : []
+    );
+
+    await handler(createArgs());
+
+    expect(mockExeca).not.toHaveBeenCalled();
+    expect(mockRunJestViaMoon).toHaveBeenCalled();
+  });
+
+  it('skips fast path for Scout test files with parallel playwright config', async () => {
+    mockResolveValidationBaseContext.mockResolvedValue({
+      ...baseContext,
+      runContext: {
+        ...baseContext.runContext,
+        changedFiles: [
+          'src/platform/plugins/shared/discover/test/scout/ui/parallel_tests/metrics_experience/fullscreen.spec.ts',
+        ],
+      },
+    });
+
+    mockExistsSync.mockReturnValue(false);
+    mockReaddirSync.mockImplementation((dir: string) =>
+      dir === '/repo/src/platform/plugins/shared/discover/test/scout/ui'
+        ? ['parallel.playwright.config.ts']
+        : []
     );
 
     await handler(createArgs());

src/dev/run_check.ts

@@ -7,7 +7,15 @@
  * License v3.0 only", or the "Server Side Public License, v 1".
  */
 
-import { existsSync } from 'fs';
+import { existsSync, readdirSync } from 'fs';
+
+const dirHasPlaywrightConfig = (dir: string): boolean => {
+  try {
+    return readdirSync(dir).some((f) => f.endsWith('playwright.config.ts'));
+  } catch {
+    return false;
+  }
+};
 import Path from 'path';
 
 import { run } from '@kbn/dev-cli-runner';
@@ -142,10 +150,7 @@ const isTestFile = (filePath: string) => TEST_FILE_RE.test(filePath);
 const findJestUnitConfig = (filePath: string): string | undefined => {
   let dir = Path.dirname(Path.resolve(REPO_ROOT, filePath));
   while (true) {
-    if (
-      existsSync(Path.join(dir, 'jest.integration.config.js')) ||
-      existsSync(Path.join(dir, 'playwright.config.ts'))
-    ) {
+    if (existsSync(Path.join(dir, 'jest.integration.config.js')) || dirHasPlaywrightConfig(dir)) {
       return undefined;
     }
     for (const configName of JEST_CONFIG_NAMES) {

src/platform/plugins/shared/discover/test/scout/ui/parallel_tests/metrics_experience/fullscreen.spec.ts

@@ -115,6 +115,7 @@ spaceTest.describe(
 
       await spaceTest.step('open context menu in fullscreen', async () => {
         await metricsExperience.clearSearch();
+        await expect(metricsExperience.pagination.container).toBeVisible();
         await metricsExperience.openCardContextMenu(0);
         await expect(metricsExperience.chartActions.viewDetails).toBeVisible();
       });