Consolidation cluster 1: codec (CPU) (long-tail epic #2424) #2425

Follow-up to epic #2424 / #2390. Cluster 1 of 16, in fanout order. This issue is parallel-safe with the other 15 cluster issues; nothing depends on it landing first.

Likely 1-2 PRs depending on review size.

Scope

Fold the CPU-side codec tests into the unit/ cluster. The aim is one parametrised home for codec round-trips plus a thin home for codec-specific edge cases.

Files to consolidate (11)

• xrspatial/geotiff/tests/test_jpeg.py
• xrspatial/geotiff/tests/test_jpeg2000.py
• xrspatial/geotiff/tests/test_lerc.py
• xrspatial/geotiff/tests/test_lerc_max_z_error.py
• xrspatial/geotiff/tests/test_lerc_valid_mask.py
• xrspatial/geotiff/tests/test_lz4.py
• xrspatial/geotiff/tests/test_lz4_compression_level_2026_05_11.py
• xrspatial/geotiff/tests/test_miniswhite_nodata_1809.py
• xrspatial/geotiff/tests/test_miniswhite_writer_roundtrip_1836.py
• xrspatial/geotiff/tests/test_signed_miniswhite_rejected_2278.py
• xrspatial/geotiff/tests/test_to_geotiff_allow_internal_only_jpeg_parity.py

Target

Extend xrspatial/geotiff/tests/unit/test_compression.py (already exists from epic #2390 PR 11) for codec round-trip cases. If the diff grows past roughly 1500 lines, split write-side round-trips into a sibling unit/test_codec_roundtrip.py.

Boundary

• GPU codec paths (test_jpeg_gpu_1549.py, test_lerc_valid_mask_gpu.py, test_nvcomp_*, test_nvjpeg*) are out of scope. They belong to the GPU cluster issue.
• Codec docstring / level tests (test_compression_docstring_1644.py, test_compression_level.py) are also in scope here; PR 11 of Epic: Consolidate the GeoTIFF test suite (354 files → ~50) #2390 left them at the top level.

Constraints (same across the epic)

• Tests-only. No changes to xrspatial/geotiff/ source modules.
• Markers from _helpers/markers.py; make_minimal_tiff from _helpers/tiff_builders.py.
• Parametrise IDs descriptively (e.g. id="lerc-float32[max-z-error=1e-6]"). No issue numbers in test names or filenames.
• CLUSTER_AUDIT_CODEC.md deleted on the pre-merge commit, not after merge.

Verification

pytest xrspatial/geotiff/tests/unit/test_compression.py -v
pytest xrspatial/geotiff/tests/ -x -q

File count drops by 10 (11 deleted, 1 added if extending existing file) or 9 (if splitting into a new sibling).