[extension] Add Quality Gates (Enforcement Layer) extension to community catalog (#3431)

* Add Quality Gates (Enforcement Layer) extension to community catalog

Add gates extension submitted by @schwichtgit to:
- extensions/catalog.community.json (alphabetical order, between fx-to-dotnet and github-issues)
- docs/community/extensions.md community extensions table

Closes #3414

Assisted-by: GitHub Copilot (model: claude-sonnet-4.6, autonomous)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix: revert unrelated catalog reformatting and remove empty changelog field from gates entry

- Restore original ordering/formatting of aide, checkpoint, critique,
  threatmodel entries and inline requires.tools objects that were
  inadvertently reordered in the previous commit
- Remove `"changelog": ""` from the gates entry (empty URL is
  inconsistent with catalog conventions; field should be omitted when
  no changelog URL exists)

Addresses review comments:
- github/spec-kit#3431 (comment) — unrelated reformatting/reordering
- github/spec-kit#3431 (comment) — empty changelog field

Assisted-by: GitHub Copilot (model: claude-sonnet-4.5, autonomous)

* Fix gates entry tool requirements: git required, add node and shellcheck optional

- Mark git as required (per v0.1.0 README: \"jq and git — the hooks and verify.sh require them\" and release notes: \"Requires Spec Kit >=0.12.0, jq, and git\")
- Add node as optional tool (per issue #3414 submission)
- Add shellcheck as optional tool (per issue #3414 submission)
- Update gates entry updated_at and top-level updated_at to 2026-07-13

Assisted-by: GitHub Copilot (model: claude-sonnet-4.5, autonomous)"

---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

docs/community/extensions.md

@@ -98,6 +98,7 @@ The following community-contributed extensions are available in [`catalog.commun
 | Project Health Check | Diagnose a Spec Kit project and report health issues across structure, agents, features, scripts, extensions, and git | `visibility` | Read-only | [spec-kit-doctor](https://github.com/KhawarHabibKhan/spec-kit-doctor) |
 | Project Status | Show current SDD workflow progress — active feature, artifact status, task completion, workflow phase, and extensions summary | `visibility` | Read-only | [spec-kit-status](https://github.com/KhawarHabibKhan/spec-kit-status) |
 | QA Testing Extension | Systematic QA testing with browser-driven or CLI-based validation of acceptance criteria from spec | `code` | Read-only | [spec-kit-qa](https://github.com/arunt14/spec-kit-qa) |
+| Quality Gates (Enforcement Layer) | Deterministic quality enforcement for Spec Kit projects at three boundaries — agent hooks, git pre-commit, CI — with one policy file and provable enforcement (attestations, canaries, verified parity). | `process` | Read+Write | [spec-gates](https://github.com/schwichtgit/spec-gates) |
 | RAG Azure Builder | Spec Kit extension for onboarding and operating an Azure RAG stack with guided workflows. | `process` | Read+Write | [spec-kit-extension-rag-azure-builder](https://github.com/Sertxito/spec-kit-extension-rag-azure-builder) |
 | Ralph Loop | Autonomous implementation loop using AI agent CLI | `code` | Read+Write | [spec-kit-ralph](https://github.com/Rubiss-Projects/spec-kit-ralph) |
 | Reconcile Extension | Reconcile implementation drift by surgically updating feature artifacts. | `docs` | Read+Write | [spec-kit-reconcile](https://github.com/stn1slv/spec-kit-reconcile) |