fix: adding gocad export for structured grid support

[lachlangrose]

No description provided.

[Copilot]

Pull request overview

Adds export/visualisation support for structured grids: GOCAD VOXET export for StructuredGrid and VTK (pyvista) export for StructuredGrid2D, with accompanying unit tests and CI dependency updates.

Changes:

• Implement StructuredGrid2D.vtk() returning a quad-cell pyvista.UnstructuredGrid.
• Add GOCAD VOXET writer for StructuredGrid and route .save() for .vo/.gocad.
• Expand unit tests for the new exports and add pyvista to the CI conda install.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
LoopStructural/interpolators/supports/_2d_structured_grid.py	Implements StructuredGrid2D.vtk() (PyVista unstructured grid with QUAD cells).
LoopStructural/export/gocad.py	Adds VOXET export implementation for StructuredGrid properties/cell_properties.
LoopStructural/datatypes/_structured_grid.py	Fixes maximum computation and adds .save() support for .vo/.gocad.
tests/unit/interpolator/test_2d_discrete_support.py	Adds VTK export assertions for 2D structured grid.
tests/unit/datatypes/test__structured_grid.py	Adds VOXET export tests for point/cell properties; minor formatting updates.
.github/workflows/tester.yml	Installs pyvista in CI so new VTK tests can run.

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