- Make LeaderElection check_interval, max_cluster_wait, and cluster_check_interval
configurable via Application env so tests can override with short values
- Slow LeaderElection tests now use 50-150ms timeouts instead of 3-6s
- Remove :slow tag from unused_test (compile cache makes reruns cheap)
- Drop :slow from test_helper exclude list
All 2490 tests now run in ~45s (up from 2485 with 5 excluded).