Cover compression_level= for compression='lz4'

[brendancol]

Summary

The compression-level validator in xrspatial.geotiff.__init__ advertises a (0, 16) valid range for lz4 alongside deflate (1, 9) and zstd (1, 22), but only the deflate and zstd ranges had round-trip + boundary-reject tests.

The lz4 path goes through the same _LEVEL_RANGES validator at three call sites (eager numpy, dask streaming, and _write_vrt_tiled). A regression that dropped 'lz4' from _LEVEL_RANGES would have silently accepted any int level: lz4_compress itself does not validate the level argument.

This adds 18 tests in xrspatial/geotiff/tests/test_lz4_compression_level_2026_05_11.py:

• Round-trip at levels 0 / 1 / 9 / 16 (lossless: assert_array_equal).
• Default no-arg path (compression_level=None falls through to the codec default).
• Higher level not larger on compressible input (level 16 file size <= level 0 file size).
• Eager out-of-range reject at -1 / -10 / 17 / 100.
• Valid-range message format pin (lz4 ... valid: 0-16).
• Dask streaming round-trip at 0 / 1 / 8 / 16 (separate validation call site).
• Dask streaming out-of-range reject at -1 / 17 / 50.

Closes the Cat 4 MEDIUM parameter-coverage gap left after pass 7 of the test-coverage sweep on geotiff. No source changes.

Test plan

• All 18 new tests pass locally
• No regressions in test_compression_level.py (14 tests) or test_lz4.py (13 tests)
• Verified the test suite would catch a regression: dropping 'lz4' from _LEVEL_RANGES makes the out-of-range tests fail (silent acceptance)

[Copilot]

Pull request overview

Adds targeted test coverage for compression='lz4' when using the compression_level= parameter in the GeoTIFF writer, ensuring the documented (0, 16) level range is enforced and that both eager and dask-streaming call sites are covered.

Changes:

• Add a new test module covering LZ4 round-trip correctness at boundary and representative levels, default compression_level=None behavior, out-of-range rejection, and dask-streaming validation.
• Update the internal sweep state CSV to record the added coverage work.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
xrspatial/geotiff/tests/test_lz4_compression_level_2026_05_11.py	New tests for LZ4 compression_level range enforcement, error messaging, and eager + dask streaming round-trips.
.claude/sweep-test-coverage-state.csv	Records the new “Pass 8” test-coverage sweep status entry for geotiff.

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