chore: include accessibility scans in non-security CI shards

Add automated accessibility suite execution to the standard non-security
end-to-end browser shards so regressions are caught during routine CI runs.

This change is necessary to enforce accessibility checks consistently across
Chromium, Firefox, and WebKit without creating a separate pipeline path.

Behavior impact:
- Non-security shard jobs now run accessibility tests alongside existing suites
- Security-specific job behavior remains unchanged
- Sharding logic remains unchanged, with only test scope expanded

Operational consideration:
- Monitor shard runtime balance after rollout; if sustained skew appears,
  split accessibility coverage into its own sharded workflow stage.

.github/workflows/e2e-tests-split.yml

@@ -980,6 +980,7 @@ jobs:
             --project=chromium \
             --shard=${{ matrix.shard }}/${{ matrix.total-shards }} \
             --output=playwright-output/chromium-shard-${{ matrix.shard }} \
+            tests/a11y \
             tests/core \
             tests/dns-provider-crud.spec.ts \
             tests/dns-provider-types.spec.ts \
@@ -1225,6 +1226,7 @@ jobs:
             --project=firefox \
             --shard=${{ matrix.shard }}/${{ matrix.total-shards }} \
             --output=playwright-output/firefox-shard-${{ matrix.shard }} \
+            tests/a11y \
             tests/core \
             tests/dns-provider-crud.spec.ts \
             tests/dns-provider-types.spec.ts \
@@ -1470,6 +1472,7 @@ jobs:
             --project=webkit \
             --shard=${{ matrix.shard }}/${{ matrix.total-shards }} \
             --output=playwright-output/webkit-shard-${{ matrix.shard }} \
+            tests/a11y \
             tests/core \
             tests/dns-provider-crud.spec.ts \
             tests/dns-provider-types.spec.ts \