docs: add CONTRIBUTING with prek hook setup

[olantwin]

The repo had no CONTRIBUTING.md. Add one documenting the pixi environment, prek hooks (pixi run install-hooks / pixi run lint), conventional commits, and testing.

Summary by CodeRabbit

• Documentation
  • Added contribution guidelines covering development setup, workflow, coding standards, commit conventions, testing and build instructions, and licensing/SPDX requirements for new files.

[olantwin]

@coderabbitai review

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Review finished.

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: ddaf2fd7-354a-4ee4-b2d0-495185f65edc

📥 Commits

Reviewing files that changed from the base of the PR and between 1653a85 and 53bae5a.

📒 Files selected for processing (1)

• CONTRIBUTING.md

🚧 Files skipped from review as they are similar to previous changes (1)

• CONTRIBUTING.md

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📝 Walkthrough

Walkthrough

Adds CONTRIBUTING.md with development workflow, coding, testing, commit, and licensing guidance for the SHiP Data Model.

Changes

Contribution Guidance

Layer / File(s)	Summary
Contribution workflow and licensing CONTRIBUTING.md	Documents pixi environment setup, prek hooks, branching, coding standards, Conventional Commits, test/build commands, and LGPL-3.0-or-later with SPDX/REUSE requirements.

Estimated code review effort: 1 (Trivial) | ~2 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the new CONTRIBUTING.md docs, though it focuses on the prek hook setup rather than the full contribution guide.
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.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch docs/prek-hooks

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@CONTRIBUTING.md`:
- Line 18: Update the SPDX guidance in CONTRIBUTING.md to require
REUSE-compliant coverage rather than requiring literal headers in every file.
Mention adding inline SPDX headers where appropriate, while aligning the wording
with the aggregate metadata configured in REUSE.toml.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: fa75abe6-ab2f-44a2-bb11-3f94bc9a9edd

📥 Commits

Reviewing files that changed from the base of the PR and between 543f568 and 1653a85.

📒 Files selected for processing (1)

• CONTRIBUTING.md

[olantwin]

@coderabbitai review

[coderabbitai]

✅ Action performed

Review finished.

Note: CodeRabbit is an incremental review system and does not re-review already reviewed commits. This command is applicable only when automatic reviews are paused.