Add RKF78 adaptive integrator

[Mtrya]

Pull Request

Description

Adds a Runge-Kutta-Fehlberg 7(8) adaptive integrator and exposes it through the Rust integrator factory, numerical propagation configuration, Python bindings, Python facade, tests, examples, and documentation.

Changelog

Added

• Add RKF78 / RKF78Integrator support for high-order adaptive integration in Rust and Python.
• Add RKF78 tests, examples, and API/reference documentation.

Changed

• Extend numerical propagation integrator selection and comparison examples to include RKF78.

Note to Reviewers

Validation run locally:

• cargo test
• uv pip install -e . && .venv/bin/python -m pytest tests/ -v
• cargo clippy --all-targets --all-features -- -D warnings
• ruff check
• ./scripts/generate_stubs.sh

[codecov]

Codecov Report

❌ Patch coverage is 96.36570% with 64 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.46%. Comparing base (3037edf) to head (04ebd68).
⚠️ Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
src/integrators/rkf78.rs	95.79%	64 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #339      +/-   ##
==========================================
- Coverage   94.88%   94.46%   -0.42%     
==========================================
  Files         186      187       +1     
  Lines       86070    87825    +1755     
==========================================
+ Hits        81666    82964    +1298     
- Misses       4404     4861     +457     

Flag	Coverage Δ
python	94.70% <ø> (ø)
python-rust	65.76% <68.57%> (-1.55%)	⬇️
rust-unit	93.83% <96.36%> (-0.42%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
brahe/integrators.py	100.00% <ø> (ø)
brahe/propagators.py	100.00% <ø> (ø)
src/integrators/butcher_tableau.rs	93.78% <100.00%> (+2.83%)	⬆️
src/integrators/traits.rs	97.41% <100.00%> (+0.06%)	⬆️
src/propagators/dnumerical_orbit_propagator.rs	95.17% <100.00%> (-1.21%)	⬇️
src/propagators/dnumerical_propagator.rs	91.43% <ø> (ø)
src/propagators/numerical_propagation_config.rs	100.00% <100.00%> (ø)
src/time/epoch.rs	98.51% <100.00%> (-0.64%)	⬇️
src/integrators/rkf78.rs	95.79% <95.79%> (ø)

... and 13 files with indirect coverage changes

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[duncaneddy]

This is awesome! It's a bit of a larger PR, so will take me a little bit to go through it all, but given your past work and all checks pass I have high confidence there won't be much if anything at all. I hope to get to it by end of week.

Thank you yet again for a great contribution to improving the package!

[duncaneddy]

Generally looks great. I pushed two small changes fixing adding the library API reference into the navbar (annoying little chore that I haven't figured out how to auto-generate while still allowing for overrides), and adding a link to the coefficient source.

Just one comment on the DynamicsEvaluationContext I'd like to have a quick discussion about or remove.