docs(release): codify /admin/* semver discipline in release contract (Story 44.4)

[ALLiDoizCode]

Summary

Story 44.4 of the Townhouse HS-Mode v1 epic. Documentation-only PR — no code, CI workflow, or TypeScript changes.

Doc edits in CONNECTOR_RELEASE_CONTRACT.md

• New ## API stability section (inserted between ## Stability guarantees and ## Supply-chain signing): semver bump rules for /admin/* field/endpoint additions and removals, ILP wire-format changes, and image architecture changes.
• ### Townhouse pin discipline subsection: describes how townhouse pins by digest in image-manifest.json and gates bumps on the SDK contract canary.
• New ## Staying current section (inserted between ## Recommended pinning strategy and ## Historical tag corruption): GitHub Watch UI (preferred) + gh api CLI (fallback) mechanisms for release notifications; automation explicitly deferred as Open Thread Epic 7 #2.
• Multi-arch sentence in ## Artifacts: adds explicit rule that adding architectures is build-only (no semver bump) and removing one is a MAJOR bump.
• Town mirror drift-detection note in ## Verification: documents how to verify body-equivalence against the toon-protocol/town mirror file.
• pull/<num> placeholder fix on two lines (Story 44.3 follow-up): both pull/<num> references for PR feat(release): cosign-sign connector + ATOR sidecar images via keyless OIDC #66 now correctly link to pull/66.

CHANGELOG.md edit

Added ### Documentation entry in [Unreleased]: Codify /admin/* semver discipline in CONNECTOR_RELEASE_CONTRACT.md (Story 44.4 / PR #). The docs(release) commit type maps to no semantic-release version bump — this PR alone does not cut a release.

Asymmetric CHANGELOG treatment (town side)

toon-protocol/town has no CHANGELOG.md at root, packages/townhouse/, or packages/sdk/ — town uses sprint-status.yaml + commit messages as its audit log. The town-side "changelog equivalent" for this story is:

1. A "See also" cross-link added to packages/sdk/CONNECTOR_MIGRATION.md pointing to the new mirror.
2. A row added to CLAUDE.md ## Where to Find Things.
3. Sprint-status comment + town PR commit message.

This asymmetry is intentional. Adding a singleton CHANGELOG.md in town for one entry would be ceremonial noise with no semantic-release pipeline to consume it.

Town-side mirror content

The body of CONNECTOR_RELEASE_CONTRACT.md will be mirrored byte-for-body-identical at packages/sdk/CONNECTOR_RELEASE_CONTRACT.md in toon-protocol/town in a companion PR. The town file prepends a 3-line comment header (drift-detection aid); the body below that header is byte-identical to this file.

Body-equivalence is verified with:

diff CONNECTOR_RELEASE_CONTRACT.md \
     <(tail -n +4 /path/to/town/packages/sdk/CONNECTOR_RELEASE_CONTRACT.md)

Expected output: empty.

Test plan

• grep -n "API stability\|Staying current" CONNECTOR_RELEASE_CONTRACT.md → section headings present
• grep -nE "pull/<num>" CONNECTOR_RELEASE_CONTRACT.md → empty (placeholder fixup confirmed)
• grep -n "Story 44.4" CHANGELOG.md → matches [Unreleased] entry
• Semantic-release dry-run: docs(release) prefix → no version bump
• Body-equivalence diff with town PR (after town PR opens): diff connector/CONNECTOR_RELEASE_CONTRACT.md <(tail -n +4 town/packages/sdk/CONNECTOR_RELEASE_CONTRACT.md) → empty

🤖 Generated with Claude Code

[github-actions]

🎉 This PR is included in version 3.6.1 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀