Clean up and fix test suites in CI

Review all test suites, delete stale, superseeded, those that were one off to check feature flags or absence of something. Kill the most long running or flaky with unit tests that execute in milliseconds. Regroup between quick and full, Fix broken tests in CI - GitHub Actions - look at a few recent test runs and fix broken/flaky tests. Babysit CI/CD until the tests (test.yaml) pass.

test.yml green (run 40819394708): fixed preflight (f) floor and CE release test under PrivateTmp runners; gated smoke at 4 workers (local A/B 409s→281s). PR #7316 merged 53b5786a2, deploy green. Deferred: e2e trim to 2–3/view (now 4.6). Memory: proposed 1 gotcha.