GEOPY-2994: Support Grid2D in grid_model_merger application

[domfournier]

GEOPY-2994 - Support Grid2D in grid_model_merger application

[Copilot]

Pull request overview

This PR extends grid_model_merger to better support Grid2D inputs by refining TreeMesh refinement logic for 2D meshes, tightening UI model type selection, and improving handling of “all NaN” model merges with a warning and a regression test.

Changes:

• Add a warning/early-exit path when no valid model values are available during merge, plus a test asserting the warning.
• Adjust refine_tree_by_mesh for Grid2D to derive refinement level from XY TreeMesh cell sizes (ignoring Z).
• Restrict selectable input model data types in the UI JSON to Float only.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
tests/run_tests/grid_model_merger_test.py	Adds coverage for the “all NaN inputs” warning path.
grid_apps/utils.py	Updates Grid2D TreeMesh refinement level calculation to use XY cell sizes.
grid_apps/grid_model_merger/driver.py	Adds “no valid values” early return + guards inverse symlog by threshold.
grid_apps-assets/uijson/grid_model_merger.ui.json	Restricts input model selection to float data types.

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