Revamp HS2P tests with deterministic mocked multires coverage

[clemsgrs]

Summary

• add a fresh test-revamped/ suite focused on deterministic TDD for WSI tiling and sampling logic
• keep legacy test/input/config.yaml and test/gt/test-wsi.npy untouched, but unused by revamped tests
• point pytest discovery and PR CI to run test-revamped as the authoritative suite

New tests

Test file	What it validates
test-revamped/test_sort_and_mask_utils.py	Deterministic coordinate dedup/sort and exact mask-coverage fractions
test-revamped/test_level_selection.py	Best-level selection (within tolerance + finer fallback) and spacing guard error path
test-revamped/test_mocked_multires_tiling.py	Exact tile coordinates/counts on mocked rectangular tissue; threshold boundary (50% vs 51%); exact coordinate shifts across target spacings
test-revamped/test_mocked_sampling_filter.py	Per-class coordinate filtering (tumor/stroma) on controlled label masks; discrete-label integrity after mask alignment/resizing
test-revamped/test_real_fixture_smoke_regression.py	Real WSI+mask smoke checks for determinism, monotonicity under stricter tissue threshold, and metadata invariants

Verification

• MPLCONFIGDIR=/tmp/mpl /Users/clems/Code/venv/hs2p/bin/python -m pytest -q test-revamped
• result: 12 passed