Formalize Continuum release contract for git-warp

[flyingrobots]

Why this matters

The v18.1 release sequence exposed that git-warp had a strong local release runbook, but not a repo-profiled Continuum release contract that can generalize across related repositories.

Evidence

• v18.1.2 required release automation and manual registry-dispatch clarification.
• The existing runbook mixed universal release doctrine with repo-specific package, registry, docs, and workflow facts.
• Post-release planning identified the missing invariant: planned, versioned releases must have a thesis before implementation scope becomes active.

Done when

• .github/RELEASE.md separates universal release contract from git-warp mechanics.
• .continuum/release.yml records repo-specific release facts.
• Release docs define retrospectives, next-release planning, release types, version selection, dist-tags, idempotency, failure handling, and release evidence.
• Release workflow instructions dispatch publication from the tag ref and verify checkout/tag alignment.
• Release/doc topology gates require the release profile.