feat: reqstool-regression — SSOT requirements repository for regression testing

[jimisola]

Context

Depends on #324 (variant investigation).

We need a Single Source of Truth (SSOT) repository containing the bulk of requirements, covering all enum permutations. Both the Python and Java regression repos will import from this repository via git location.

Proposed structure

A new repo reqstool/reqstool-regression containing:

• 7+ requirements covering:

  • All 3 significance levels: shall, should, may
  • All 4 lifecycle states: draft, effective, deprecated, obsolete
  • All 9 categories: functional-suitability, performance-efficiency, compatibility, interaction-capability, reliability, security, maintainability, flexibility, safety
  • Both implementation types: in-code, N/A

• 9 SVCs covering all 5 verification types: automated-test, manual-test, review, platform, other

  • If variant is removed (feat: investigate removing variant (system/microservice/external) #324), SVCs can live directly in this repo

• Referenced by reqstool-regression-python and reqstool-regression-java via git location

Relationship to other issues

• Depends on: feat: investigate removing variant (system/microservice/external) #324 (determines whether SVCs can live here or must be in the wrappers)
• Depended on by: reqstool-regression-python, reqstool-regression-java

Acceptance criteria

• New repo reqstool/reqstool-regression created
• requirements.yml with full enum coverage
• SVCs file (if variant removal allows it)
• README documenting enum coverage matrix
• CI validates YAML against schemas