test: exercise repository check selector exclusions [DO NOT MERGE]

.agents/checks/CRAB-FIXTURE-01/CHECK.md

@@ -18,6 +18,8 @@ hints:
 
 # Synthetic review fixtures
 
+<!-- Integration control: documentation-only change; policy behavior is unchanged. -->
+
 Review the eligible JSON changes for accidentally committed credentials, private
 documents, or real personal data. Fixture records must use clearly synthetic
 values. Keep the assessment within the assigned files and the repository's

tests/repository-checks/README.md

@@ -21,3 +21,6 @@ The integration test should verify:
 A clean result is expected. These fixtures must not contain real secrets, expose a
 service, execute commands, or introduce a vulnerability. A clean GitHub comment
 alone does not prove that the optional check loaded; confirm that in the trace.
+
+Selector control: mentioning `"review_fixture_version"` in this Markdown file
+does not make it an eligible JSON fixture.

tests/repository-checks/fixture.json

@@ -4,7 +4,7 @@
   "records": [
     {
       "record_id": "sample-a",
-      "display_name": "Synthetic Sample A"
+      "display_name": "Synthetic Sample A - selector control"
     }
   ]
 }