feat(output): publish EventHeader from every generator source

[matclim]

Checklist

• Commit message follows conventional commits
• Pre-commit checks pass (pixi run lint)
• CI checks pass

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Summary by CodeRabbit

• New Features

  • Added event metadata and provenance information to simulation output files.
  • Particle sources can now provide event headers; empty headers are supplied when unavailable.
  • Both Monte Carlo and full simulation outputs now include event header data.

• Bug Fixes

  • Preserved complete-event filtering for full simulation outputs when no detector hits are present.

• Documentation

  • Documented event metadata headers and provenance fields.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: edb156db-230c-4f76-86fc-ca63c19bd169

📥 Commits

Reviewing files that changed from the base of the PR and between d6e7893 and 87ba937.

⛔ Files ignored due to path filters (1)

• pixi.lock is excluded by !**/*.lock

📒 Files selected for processing (3)

• pixi.toml
• src/mc_particle_source.hpp
• src/sim_output_module.cpp

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📝 Walkthrough

Walkthrough

The change raises the shipdatamodel requirement and adds SHiP::EventHeader production, propagation, and persistence for MC-only and full-simulation outputs.

Changes

Event header support

Layer / File(s)	Summary
Provider event-header contract pixi.toml, src/mc_particle_source.hpp	The dependency requirement is raised to >=0.4. The particle source helper adds optional event-header generation and publishes a default header when no generator is supplied.
MC output header writing src/sim_output_module.cpp	The MC-only RNTuple stores and writes SHiP::EventHeader. Its input family now requires the event-header product.
Full-simulation header writing src/sim_output_module.cpp	The full-simulation RNTuple stores and writes SHiP::EventHeader. Empty-hit filtering remains before pool acquisition.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Mergeability Score: ⚪ Minimal · up to 87ba9

This localized change has no actionable merge-blocking risk in the supplied evidence and is merge-ready after normal checks and review.

Suggested reviewers: olantwin

Sequence Diagram(s)

sequenceDiagram
  participant ParticleSource
  participant EventHeaderProduct
  participant MCOutputWriter
  participant SimOutputWriter

  ParticleSource->>EventHeaderProduct: publish SHiP::EventHeader
  EventHeaderProduct->>MCOutputWriter: provide event_header with mc_particles
  MCOutputWriter->>MCOutputWriter: bind header and write RNTuple entry
  EventHeaderProduct->>SimOutputWriter: provide event_header with mc_particles and sim_results
  SimOutputWriter->>SimOutputWriter: filter empty hits, bind header, and write entry

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🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly describes the primary change: publishing EventHeader from every generator source.
Description check	✅ Passed	The description includes the required Checklist section and confirms all listed checks are complete.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch pr/event-header

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[github-actions]

✅ prek hooks passed

[github-actions]

Physics Metrics Comparison

All configurations match reference (no significant differences)

• Configurations compared: 1
• Matching reference: 1

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About this comparison

Physics metrics are extracted from ROOT files and compared.
Default comparison uses 5% tolerance for histogram statistics
and 3σ for fit parameters.

Metrics stored in git notes: refs/notes/ci/physics-metrics/<config>

[olantwin]

Please make prek happy. Apart from that, this looks good for merging.

[olantwin]

Some other generators will probably need updating, e.g. genie and the file sources. I'll do those in a follow-up PR.