Spike: CI golden-vector gate + tag-release

[grootstebozewolf]

Summary

• Adds a CI gate on main/PRs: csharp, java, and typescript golden-vector tests against committed data/golden_vectors.json.
• Adds a tag-release workflow: push of v* creates a GitHub Release (DOI 10.5281/zenodo.20128415).
• Coq, benches, PDF, and ProRail refetch stay out of the default gate.

Out of this spike

• No version bump (CITATION 1.1.0 vs packages 1.0.0 vs tag v1.0.3).
• No merge. No new tag. v1.0.3 still has no GitHub Release until someone tags again or creates it by hand.

Test plan

• PR CI goes green on csharp / java / typescript
• Do not merge until green