Add Architecture Governance extension to community catalog

Add arch-governance extension submitted by @ashbrener to:
- extensions/catalog.community.json (alphabetical order)
- docs/community/extensions.md community extensions table

Closes #4084

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

Author: github-actions[bot]

docs/community/extensions.md

@@ -32,6 +32,7 @@ The following community-contributed extensions are available in [`catalog.commun
 | Analytics | Measure what your AI builds, and how much time it saves you | `visibility` | Read+Write | [spec-kit-analytics](https://github.com/Fyloss/spec-kit-analytics) |
 | API Evolve | Managed API contract evolution — breaking-change detection, semver enforcement, deprecation orchestration, and lifecycle gates across REST, GraphQL, and gRPC | `process` | Read+Write | [spec-kit-api-evolve](https://github.com/Quratulain-bilal/spec-kit-api-evolve) |
 | Architect Impact Previewer | Predicts architectural impact, complexity, and risks of proposed changes before implementation. | `visibility` | Read-only | [spec-kit-architect-preview](https://github.com/UmmeHabiba1312/spec-kit-architect-preview) |
+| Architecture Governance | Keep specs, code & ADRs in sync: citation slots + a read-only, fail-closed validator | `docs` | Read+Write | [spec-kit-arch-governance](https://github.com/ashbrener/spec-kit-arch-governance) |
 | Architecture Guard | Framework-agnostic architecture review extension for validating implementation against governance and architecture constitutions, detecting architectural drift, and generating non-blocking refactor tasks | `process` | Read+Write | [spec-kit-architecture-guard](https://github.com/DyanGalih/spec-kit-architecture-guard) |
 | Architecture Workflow | Generate or reverse project-level 4+1 architecture views with per-view and full-workflow commands | `docs` | Read+Write | [spec-kit-arch](https://github.com/bigsmartben/spec-kit-arch) |
 | Archive Extension | Archive merged features into main project memory, resolving gaps and conflicts. | `docs` | Read+Write | [spec-kit-archive](https://github.com/stn1slv/spec-kit-archive) |

extensions/catalog.community.json

@@ -1,6 +1,6 @@
 {
   "schema_version": "1.0",
-  "updated_at": "2026-08-13T00:00:00Z",
+  "updated_at": "2026-08-14T00:00:00Z",
   "catalog_url": "https://raw.githubusercontent.com/github/spec-kit/main/extensions/catalog.community.json",
   "extensions": {
     "adrkit": {
@@ -286,6 +286,44 @@
       "created_at": "2026-05-14T00:00:00Z",
       "updated_at": "2026-06-30T00:00:00Z"
     },
+    "arch-governance": {
+      "name": "Architecture Governance",
+      "id": "arch-governance",
+      "description": "Keep specs, code & ADRs in sync: citation slots + a read-only, fail-closed validator.",
+      "author": "Ash Brener",
+      "version": "1.2.2",
+      "download_url": "https://github.com/ashbrener/spec-kit-arch-governance/archive/refs/tags/v1.2.2.zip",
+      "repository": "https://github.com/ashbrener/spec-kit-arch-governance",
+      "homepage": "https://github.com/ashbrener/spec-kit-arch-governance",
+      "documentation": "https://github.com/ashbrener/spec-kit-arch-governance/blob/main/README.md",
+      "changelog": "https://github.com/ashbrener/spec-kit-arch-governance/blob/main/CHANGELOG.md",
+      "license": "MIT",
+      "category": "docs",
+      "effect": "read-write",
+      "requires": {
+        "speckit_version": ">=0.1.0",
+        "tools": [
+          { "name": "python", "version": ">=3.11", "required": true },
+          { "name": "uv", "required": true }
+        ]
+      },
+      "provides": {
+        "commands": 6,
+        "hooks": 3
+      },
+      "tags": [
+        "architecture",
+        "governance",
+        "adr",
+        "citations",
+        "spec-sync"
+      ],
+      "verified": false,
+      "downloads": 0,
+      "stars": 0,
+      "created_at": "2026-08-14T00:00:00Z",
+      "updated_at": "2026-08-14T00:00:00Z"
+    },
     "architect-preview": {
       "name": "Architect Impact Previewer",
       "id": "architect-preview",