Fix the grid_3d notebook

[munechika-koyo]

Key changes:

• Fix the grid_3d notebook to show in document
• Change plotly renderer to png to reduce the notebook output size
• Fix docstrings
• Rename notebooks to arrange intentionally

[Copilot]

Pull request overview

This PR updates the Sphinx documentation example notebooks and gallery configuration so the rendered docs include the intended notebook set/order, while also reducing Plotly output size and fixing notebook text/docstrings.

Changes:

• Adjusts the examples gallery configuration (removing :reversed:) and adds/renames multiple documentation notebooks.
• Updates Plotly usage in notebooks (e.g., renderer changes in grid_3d.ipynb) and tweaks notebook visuals.
• Minor docstring cleanup in load_core_plasma() documentation.

Reviewed changes

Copilot reviewed 3 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/cherab/imas/plasma/core.py	Docstring cleanup for load_core_plasma() parameter documentation.
docs/source/examples.md	Updates notebook gallery directive options/order.
docs/notebooks/radiation/radiation_3d.ipynb	Adds a new 3D radiation emitter example notebook.
docs/notebooks/radiation/grid_3d.ipynb	Tweaks Plotly rendering/layout to improve doc rendering/output size.
docs/notebooks/plasma/1_equilibrium.ipynb	Adds a plasma equilibrium example notebook.
docs/notebooks/plasma/2_edge_plasma.ipynb	Adds an edge plasma profiles example notebook.
docs/notebooks/plasma/3_full_plasma.ipynb	Adds a full plasma (core+edge) example notebook.
docs/notebooks/plasma/4_emission.ipynb	Adds an emission models example notebook.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.55%. Comparing base (816de95) to head (fd6d22e).
⚠️ Report is 7 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #36   +/-   ##
=======================================
  Coverage   69.55%   69.55%           
=======================================
  Files          52       52           
  Lines        3291     3291           
  Branches      526      526           
=======================================
  Hits         2289     2289           
  Misses        766      766           
  Partials      236      236           

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