Strengthen grid parser format checks

[rajeeja]

Closes #238 by tightening internal grid format detection and adding focused parser tests.

[Copilot]

Pull request overview

Tightens _parse_grid_type format detection by introducing per-format helper checks and adds targeted tests to ensure supported formats are correctly identified while incomplete signals are rejected.

Changes:

• Added helper predicates (_is_exodus, _is_scrip, _is_mpas, etc.) and refactored _parse_grid_type to use them.
• Expanded supported-format detection to include additional grid specs (e.g., GEOS-CS, ICON, FESOM2) via stricter checks.
• Added new unit tests covering supported formats, structured grids, and rejection of incomplete format signals.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
uxarray/io/utils.py	Adds per-format detection helpers and refactors _parse_grid_type to use stricter, format-specific checks.
test/io/test_utils.py	Adds focused tests for correct format detection and for rejecting incomplete/ambiguous datasets.

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[Copilot]

The _parse_grid_type docstring is out of sync with the implementation: it mentions only UGrid/SCRIP/Exodus/ESMF/shapefile support, but the function now also detects MPAS, GEOS-CS, ICON, FESOM2, and Structured (and there is no shapefile branch here). It also describes returning only mesh_type: str, while the function returns a 3-tuple (mesh_type, lon_name, lat_name). Please update the docstring accordingly so callers/tests have an accurate contract.