Formalize the skill release process with the evaluator as a mandatory gate

[tph-kds]

Context: skills/deckforge-skill-evaluator (added 3.1.0) runs deterministic outcome comparisons between baseline, current, and candidate skills.

Gap: nothing makes evaluator results mandatory before a release, and there is no documented release checklist or version-bump policy.

Acceptance:

• Documented release checklist covering: schema checks, layout audit, output-contract validation, build, behavioral checks, bundle validation, and evaluator results.
• Release gate: a candidate skill cannot ship without a passing evaluator run against core eval cases.
• Version-bump policy (major/minor/patch) with the changelog requirement.
• Process documented in docs/EXTENDING.md or a new release-process doc.

[tph-kds]

Resolved. Delivered and merged via PR #23 (squash commit 22ca8b3) on 2026-08-09.

• Evidence: check_release_gate.py + RELEASE_PROCESS.md + evaluator as mandatory gate (commit c8978ec)
• Plan: docs/superpowers/plans/2026-08-07-backlog-resolution.md