✨ Enhance plasma and radiation data handling with 3D visualization support

[munechika-koyo]

Key changes include:

• Improved grid subset handling in plasma loading functions.

• Added 3D grid visualization notebook for ITER JOREK data.

• Updated dependencies for enhanced visualization capabilities.

• Implemented re-slicing of IDS with fallback handling.

• Added unit tests for new functionalities and fixed charge type conversion issues.

• Updated documentation and changelog for version 0.5.0 release.

[Copilot]

Pull request overview

This PR expands the project’s radiation + plasma tooling to better support ITER JOREK-style 3D workflows, including new radiation IDS loaders, an emitter factory, improved IDS time-slicing fallback behavior, and accompanying docs/notebooks and tests.

Changes:

• Add radiation IDS accessors + a load_radiation_emitter() entrypoint that can use either emissivity values or Fourier-Bezier coefficients.
• Improve IDS time-slice fallback by re-slicing through the IMAS memory backend when get_slice() is unavailable.
• Add 3D visualization notebooks and update test fixtures/dependencies to support the new workflows.

Reviewed changes

Copilot reviewed 26 out of 26 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
tests/test_ids_time_slice.py	Adds unit tests for get_ids_time_slice() fallback + re-slicing behavior.
tests/plasma/conftest.py	Removes duplicate plasma dataset fixtures (now centralized).
tests/ggd/conftest.py	Removes duplicated dataset copy fixtures (now centralized).
tests/emitter/test_radiation.py	Adds tests covering radiation emitter loading + coefficient reconstruction.
tests/conftest.py	Centralizes dataset-to-tmp copying fixtures for multiple test suites.
src/cherab/imas/plasma/edge.py	Adjusts grid subset handling and charge usage in edge plasma loading.
src/cherab/imas/plasma/core.py	Adjusts charge usage in core plasma loading.
src/cherab/imas/plasma/blend.py	Adjusts grid subset handling and charge usage in blended plasma loading.
src/cherab/imas/math/functions/fourier_bezier.pyx	Ensures coefficient arrays are C-contiguous; fixes LaTeX line breaks.
src/cherab/imas/math/functions/fourier_bezier.pxd	Removes unused NumPy cimport.
src/cherab/imas/ids/radiation/load_radiation.py	Introduces radiation emissivity/coefficients loaders.
src/cherab/imas/ids/radiation/__init__.py	Exposes radiation IDS loader APIs.
src/cherab/imas/ids/common/slice.py	Adds memory-backend re-slicing fallback when get_slice() is unavailable.
src/cherab/imas/ggd/unstruct_3d_mesh.py	Clarifies interpolator cache docstrings.
src/cherab/imas/ggd/unstruct_2d_mesh.py	Clarifies interpolator cache docstrings.
src/cherab/imas/ggd/unstruct_2d_extend_mesh.py	Clarifies interpolator cache docstrings.
src/cherab/imas/ggd/base_mesh.py	Documents interpolator cache modes and defaults.
src/cherab/imas/emitter/radiation.py	Adds load_radiation_emitter() for values/coefficients/auto emissivity sources.
src/cherab/imas/emitter/__init__.py	Exposes emitter public API.
pixi.toml	Adds visualization dependencies for 3D workflows.
docs/source/examples.md	Adds radiation notebook gallery section.
docs/source/conf.py	Adds PyVista intersphinx mapping.
docs/notebooks/radiation/grid_3d.ipynb	Adds 3D grid visualization notebook (ITER JOREK).
docs/notebooks/radiation/3d_radiation.ipynb	Adds 3D radiation emitter visualization notebook.
CHANGELOG.md	Updates changelog for v0.5.0 release items/date.
.binder/environment.yml	Adds binder deps needed for new notebooks.

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[codecov]

Codecov Report

❌ Patch coverage is 60.00000% with 78 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.55%. Comparing base (d9b987a) to head (816de95).

Files with missing lines	Patch %	Lines
src/cherab/imas/ids/radiation/load_radiation.py	29.41%	37 Missing and 11 partials ⚠️
src/cherab/imas/emitter/radiation.py	74.35%	14 Missing and 6 partials ⚠️
src/cherab/imas/plasma/blend.py	44.44%	4 Missing and 1 partial ⚠️
src/cherab/imas/plasma/edge.py	44.44%	4 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #35      +/-   ##
==========================================
- Coverage   70.10%   69.55%   -0.56%     
==========================================
  Files          48       52       +4     
  Lines        3111     3291     +180     
  Branches      491      526      +35     
==========================================
+ Hits         2181     2289     +108     
- Misses        711      766      +55     
- Partials      219      236      +17     

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