- Restructure tests.yml: install once per Python version, share .venv
via artifact instead of 32 independent installs
- Reduce test groups from 8 to 4 (tests only take ~60s per group)
- Only test Python 3.12+3.13 on PRs; full matrix on push to main
- Switch all workflows from manual actions/cache to setup-uv built-in
caching, eliminating cache race conditions
- Add --frozen flag to uv sync for deterministic CI installs
- Re-enable duration-based test splitting with least_duration algorithm
(was disabled due to a bug in the path filter)
- Fix update-test-durations path filter (tests/**/*.py never matched
actual test dirs under lib/)
- Add concurrency group with cancel-in-progress for PR runs
- Add gate jobs to satisfy existing branch protection required checks
