Consolidation cluster 8: overview (long-tail epic #2424)

[brendancol]

Follow-up to epic #2424 / #2390. Cluster 8 of 16. Parallel-safe.

Likely 1-2 PRs depending on how the write-side vs read-side split lands.

Scope

The overview surface still has 10 files at the top level. Splits naturally between write-side (extends existing write/test_overview.py) and read-side (new read/test_overview.py).

Files to consolidate (10)

Write-side -> extend write/test_overview.py

• test_overview_block_order_2308.py
• test_overview_filter.py
• test_overview_levels_decimation_factors_1766.py
• test_overview_nodata_inheritance_1739.py
• test_overview_pixel_is_point_1642.py
• test_overview_resampling_min_max_median_2026_05_11.py
• test_mode_overview_perf.py (performance smoke; keep in write/ or split into bench/ if the project has one)

Read-side -> new read/test_overview.py

• test_overview_geo_inheritance_1640.py
• test_overview_level_type_validation_2074.py
• test_overview_level_validation_backends_2160.py

Boundary

GPU overview tests (test_gpu_writer_overview_inplace_1948.py, test_gpu_writer_overview_mode_and_compression_level_1740.py) belong to the GPU cluster issue.

Constraints

• Tests-only.
• Markers from _helpers/markers.py; make_minimal_tiff from _helpers/tiff_builders.py.
• Descriptive IDs.
• CLUSTER_AUDIT_OVERVIEW.md deleted before merge.

Verification

pytest xrspatial/geotiff/tests/write/test_overview.py -v
pytest xrspatial/geotiff/tests/read/test_overview.py -v
pytest xrspatial/geotiff/tests/ -x -q

File count drops by 9 if split into two files, by 10 if everything folds into the existing write-side file.