[nawaaaaaAaar]

Refs #461.

The reported dataset shape now round-trips on current xarray 2026.9.0 and on the declared minimum xarray 2024.7.0. I could not reproduce the old failure on either supported version, so this PR intentionally makes no decoder implementation change and does not claim a newly fixed bug.

Instead, preserve the issue's useful compatibility case as regression coverage:

• Data variables share the latitude dimension, longitude dimension, or both with MultiIndex levels.
• The full Dataset, including data-variable attributes, must round-trip identically.
• Decoding must not mutate the encoded input.

Verification:

• Coding suite: 17 passed on both tested xarray versions.
• Full suite on xarray 2026.9.0: 304 passed, 1 skipped.
• Relevant pre-commit hooks and git diff --check.

This is an AI-assisted test/triage contribution. The issue's closure remains a maintainer decision; the evidence above is limited to the two recorded environments.

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

An organization owner can choose the repository organization as the billing source for reviews requested by members with a paid Copilot license. Learn about Copilot code review billing.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.13%. Comparing base (a9cebee) to head (027f24b).
⚠️ Report is 132 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #679      +/-   ##
==========================================
+ Coverage   85.78%   87.13%   +1.35%     
==========================================
  Files          13       16       +3     
  Lines        2364     3351     +987     
  Branches      183      313     +130     
==========================================
+ Hits         2028     2920     +892     
- Misses        303      385      +82     
- Partials       33       46      +13     

Flag	Coverage Δ
mypy	46.07% <ø> (+7.54%)	⬆️
unittests	92.84% <ø> (-1.15%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.