fix: do not automatically generate header id in RDF patch generation and fix missing fullstop

[recalcitrantsupplant]

Summary of changes

Fixes a bug in PatchSerializer where the H prev header line missed a trailing period. Also, header_id is now treated as optional; the H id line is only written if header_id is provided, removing the previous default UUID generation. This change is backwards compatible and primarily addresses a formatting issue and refines header generation.

Checklist

• Checked that there aren't other open pull requests for the same change.
• Checked that all tests and type checking passes.
• If the change has a potential impact on users of this project:
  • Added or updated tests that fail without the change.
  • [N/A] Updated relevant documentation to avoid inaccuracies.
• Considered granting push permissions to the PR branch,
  so maintainers can fix minor issues and keep your PR up to date.