Review and fix test suites and CI failures

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.

Sorted all 21 red test.yml runs by cause: each is fixed on develop, and CI is green on develop and on this branch. Added a ~1s quick-tier check for the top cause (task refs and dangling paths in mirrored files), merged as #7440; Jaah Deploy passed. Sweeps found no stale tests. The migration-test retirement is deferred: the cp-psql-reader credential was refused.