Add Test Coverage Drift Control extension to community catalog (#3607)

Add test-coverage-drift-control extension submitted by @benizzio to:
- extensions/catalog.community.json (alphabetical order)
- docs/community/extensions.md community extensions table

Closes #3600

Assisted-by: GitHub Copilot (model: claude-sonnet-4.6, 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>

extensions/catalog.community.json

@@ -1,6 +1,6 @@
 {
   "schema_version": "1.0",
-  "updated_at": "2026-07-17T00:00:00Z",
+  "updated_at": "2026-07-21T00:00:00Z",
   "catalog_url": "https://raw.githubusercontent.com/github/spec-kit/main/extensions/catalog.community.json",
   "extensions": {
     "aide": {
@@ -4342,6 +4342,40 @@
       "created_at": "2026-05-20T00:00:00Z",
       "updated_at": "2026-05-20T00:00:00Z"
     },
+    "test-coverage-drift-control": {
+      "name": "Test Coverage Drift Control",
+      "id": "test-coverage-drift-control",
+      "description": "Generate incremental coverage drift reports and planned remediation tasks after implementation",
+      "author": "Igor Benicio de Mesquita",
+      "version": "0.3.0",
+      "download_url": "https://github.com/benizzio/spec-kit-test-coverage-drift-control/archive/refs/tags/v0.3.0.zip",
+      "repository": "https://github.com/benizzio/spec-kit-test-coverage-drift-control",
+      "homepage": "https://github.com/benizzio/spec-kit-test-coverage-drift-control",
+      "documentation": "https://github.com/benizzio/spec-kit-test-coverage-drift-control#readme",
+      "changelog": "https://github.com/benizzio/spec-kit-test-coverage-drift-control/blob/main/CHANGELOG.md",
+      "license": "MIT",
+      "category": "code",
+      "effect": "read-write",
+      "requires": {
+        "speckit_version": ">=0.2.0"
+      },
+      "provides": {
+        "commands": 2,
+        "hooks": 1
+      },
+      "tags": [
+        "analysis",
+        "coverage",
+        "testing",
+        "quality",
+        "maintenance"
+      ],
+      "verified": false,
+      "downloads": 0,
+      "stars": 0,
+      "created_at": "2026-07-21T00:00:00Z",
+      "updated_at": "2026-07-21T00:00:00Z"
+    },
     "time-machine": {
       "name": "Time Machine",
       "id": "time-machine",