perf(ci): parallelize coverage and web snapshots in-job

.github/workflows/ci.yml

@@ -121,11 +121,10 @@ jobs:
           || 'dsh-ubuntu-24-04-16core' }}
     name: node 24 / coverage
     env:
-      # The hosted 16-core runner uses six coverage workers. The failover pool
-      # shares one 64-core VM across six always-on runner instances, so each
-      # instance may use eight while keeping the worst case at 8 × 6 = 48
-      # workers; process-bound suites remain isolated in forks.
-      DSH_COVERAGE_MAX_WORKERS: ${{ vars.DSH_CI_FAILOVER_LINUX == 'selfhosted' && github.event.pull_request.user.login != 'dependabot[bot]' && '8' || '6' }}
+      # Partitioning replaces the instrumented share; this budget gives the
+      # exempt-heavy gate two workers on both hosted and failover runners.
+      DSH_COVERAGE_MAX_WORKERS: '6'
+      DSH_COVERAGE_PARTITIONS: '4'
       DSH_GATE_CONCURRENCY: '3'
     steps:
       - uses: actions/checkout@v6
@@ -188,6 +187,7 @@ jobs:
       DSH_NODE_COMPAT_SKIP_TYPECHECK: '1'
       DSH_OXLINT_THREADS: '8'
       DSH_PUBLINT_CONCURRENCY: '8'
+      DSH_WEB_SNAPSHOT_WORKERS: '6'
       # Failover halves snapshot concurrency for the shared 64-core VM.
       DSH_SNAPSHOT_MAX_CONCURRENCY: ${{ vars.DSH_CI_FAILOVER_LINUX == 'selfhosted' && github.event.pull_request.user.login != 'dependabot[bot]' && '12' || '32' }}
     steps:
@@ -454,12 +454,12 @@ jobs:
     name: windows node 24 / native complete
     timeout-minutes: 120
     env:
-      DSH_COVERAGE_MAX_WORKERS: '2'
+      DSH_COVERAGE_MAX_WORKERS: '6'
+      DSH_COVERAGE_PARTITIONS: '8'
       # Instrumented process and polling fixtures can exceed Vitest's defaults
       # under the complete lane's concurrent gate load.
       DSH_COVERAGE_TEST_TIMEOUT_MS: '30000'
-      DSH_GATE_CONCURRENCY: '2'
-      DSH_PUBLINT_CONCURRENCY: '8'
+      DSH_GATE_CONCURRENCY: '4'
     steps:
       - uses: actions/checkout@v6
         with: