Reverts 4 commits (8139911c,282f3aff,b3aca96d,dad61e4e) that tried to workaround slow CI by limiting data subsets and cleaning caches. The real issue is debug-mode .dbn.zst parsing taking minutes. Kept: --test-threads=1 fix (root cause), hard CUDA error, action range fixes, #[ignore] for heavy tests. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>