ci: reduce Cypress parallelism from 6 shards to 2 (#40717)

Co-authored-by: Claude Code <noreply@anthropic.com>

.github/workflows/superset-e2e.yml

@@ -61,9 +61,14 @@ jobs:
       # https://github.com/cypress-io/github-action/issues/48
       fail-fast: false
       matrix:
-        parallel_id: [0, 1, 2, 3, 4, 5]
+        parallel_id: [0, 1]
         browser: ["chrome"]
         app_root: ${{ github.event_name == 'push' && fromJSON('["", "/app/prefix"]') || fromJSON('[""]') }}
+        # The /app/prefix variant (push events only) is smoke-tested on a single
+        # shard rather than the full matrix, so exclude it from the other shards.
+        exclude:
+          - parallel_id: 1
+            app_root: "/app/prefix"
     env:
       SUPERSET_ENV: development
       SUPERSET_CONFIG: tests.integration_tests.superset_test_config
@@ -141,7 +146,7 @@ jobs:
         env:
           CYPRESS_BROWSER: ${{ matrix.browser }}
           PARALLEL_ID: ${{ matrix.parallel_id }}
-          PARALLELISM: 6
+          PARALLELISM: 2
           CYPRESS_RECORD_KEY: ${{ secrets.CYPRESS_RECORD_KEY }}
           NODE_OPTIONS: "--max-old-space-size=4096"
         with: