HDF5 documentation

[The9Cat]

What

While it was fresh, I thought it best to document the recent HDF5 initialization changes implemented in EXP-code/EXP#224. Seemed like a good time to provide a full documentation for the EXP HDF5 file format intended to replace the older native PSP format.

[Copilot]

Pull request overview

Adds and updates documentation to describe EXP’s HDF5 phase-space output format and related initialization/utility workflows, alongside a small Sphinx configuration tweak and tutorial notebook refresh.

Changes:

• Added a new topics/output_hdf5.rst page documenting the HDF5 snapshot structure and recommended reader behavior.
• Updated topics/exp-phase-space.rst to describe HDF5 initialization schema and tools, and to link to the new HDF5 output docs.
• Updated Sphinx config and a tutorial notebook to reflect current docs/build layout and pyEXP usage/output.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 11 comments.

File	Description
topics/output_hdf5.rst	New documentation page describing the EXP HDF5 snapshot schema and reader guidance.
topics/exp-phase-space.rst	Expanded phase-space docs with HDF5 initialization schema and updated utilities/recommendations.
intro/Tutorials/Part1-Coefficients.ipynb	Tutorial notebook updates (version info output, units writeout, output text changes).
conf.py	Doc build metadata bump and expanded exclude_patterns (now excluding exp_repo/**).

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[michael-petersen]

This is great, thanks. My only question is when we merge this in, since the feature will linger in EXP/devel for some time, but we want the docs to be available somehow -- perhaps the solution is just to add banners saying this is only in 7.11?