v0.19.1 — local-only release bulletproofing (skill flow + pk-doctor release_integrity)

Local-only release bulletproofing — no CI workflows. Addresses the
v0.19.0 post-mortem finding that a tag push does not create a GitHub
Release. Supersedes DEC-20260422_0926-MerryArch (CI workflow
approach, rejected on vendor-lock + cost grounds) with
DEC-20260422_1348-SnowyWolf (skill flow + doctor detection).

Added

• feat(pk-doctor): 6th check category release_integrity — walks every local v* git tag, probes GitHub via gh release view for a matching Release, and WARNs on any tag without one. INFO when gh is unavailable or the tag set is empty. Opt-out via PK_DOCTOR_SKIP_RELEASE_INTEGRITY=1; tag-scan cap via PK_DOCTOR_RELEASE_INTEGRITY_MAX (default 50). Each WARN carries a ready-to-paste gh release create <TAG> command with CHANGELOG extraction inlined. See DEC-20260422_1348-SnowyWolf-local-only-release-bulletproofing.

Changed

• chore(release-semver): collapse /pk-release into a single bulletproof flow. SKILL.md (both trees) rewritten with a 9-step recipe that prepares, publishes, and verifies in one turn — the release is not considered complete until gh release view vX.Y.Z succeeds (step 8). /pk-publish retained as a recovery alias for historical tags that are missing a Release. New Gotcha: "git push --tags is not a GitHub Release." Closes BACK-20260422_0925-MightyOtter-v0-19-1-release.

Fixed

• fix(release flow): v0.19.0 tag was pushed without a corresponding GitHub Release — the prepare phase of release-semver completed but the publish phase was skipped. v0.19.0 Release was created manually; v0.19.1 ships the prevention (collapsed flow) and detection (release_integrity check) mechanisms.

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