Adopt shared governance repo; draft spec 051 (registry extraction)

[enricopiovesan]

Summary

Adopts shared org-wide governance from traverse-framework/.github (constitution mirrored + pointer note, quality-standards/antipatterns/compatibility-policy/exception-process converted to thin pointers where safe, CONTRIBUTING/CLAUDE updated) and drafts specs/051-registry-extraction/spec.md — the decision record for moving crates/traverse-registry to traverse-framework/registry.

Governing Spec

• 001-foundation-v0-1

Project Item

• Issue Draft spec 051 (registry extraction) + adopt shared governance repo #521 (Project 1)

What Changed

• Contracts changed: none
• Runtime behavior changed: none
• Compatibility impact: none — documentation/governance only
• ADR needed or linked: specs/051-registry-extraction/spec.md serves as the decision record for the upcoming registry extraction (implementation tracked separately, blocked on this spec's approval)

Validation

• bash scripts/ci/repository_checks.sh passes
• Spec alignment checked
• Contract alignment checked (n/a, no contract changes)
• Tests updated and passing (n/a, docs-only)
• Core coverage preserved (n/a)
• Required validation gates passing