Goalpost: v19 release-system activation

[flyingrobots]

Thesis slice

Make the new release process operational before v19 implementation accelerates.

Owns

• Formalize Continuum release contract for git-warp #688
• Make release guards consume the Continuum release profile #689
• unmilestoned issue bucket triage

Acceptance evidence

• Release contract PR merged.
• Release profile is required by docs topology and release guards.
• Release guard consumes profile-owned facts or has a tracked replacement for each duplicated fact.
• v19 milestone has thesis, goalposts, must-ship/may-slip/not-included scope, and a sane issue bucket.

[flyingrobots]

Goalpost complete. Acceptance evidence:\n\n- Release contract PR merged via #698.\n- Release profile is required by docs topology and release guards through .continuum/release.yml, scripts/release-profile.ts, scripts/check-docs-topology.sh, and scripts/release-guard.sh.\n- Release guard now consumes profile-owned version sources/docs topology or has repo mechanics recorded in the profile.\n- v19.0.0 milestone has a thesis, must-ship/may-slip/not-included scope, goalpost issues, and release bucket triage.\n- #688, #689, #699, and #692 are closed.\n\nClosing #693 and moving active v19 work to #694.