test(11.1-06): plant one fixture per docs checker rule and run them in the gate

- testdata/clean passes every check; 63 violation cases each overlay one
  fault and a want.txt naming the single problem it must produce
- TestPlantedViolations also plants the forbidden name (split literals)
  and symlink escapes at run time; TestBuildOutputGuard covers --out
- check-phase11.1.sh --self-test runs the corpus through a go test -json
  detector that refuses FAIL, SKIP, zero tests and no tests to run
- the self-test scratch copy now carries examples/ and README.md, so its
  baseline sees the example command literals the real tree sees

internal/docsite/testdata/clean/docs/guide/config.md

@@ -0,0 +1,20 @@
+---
+title: Config
+description: "Configure the demo database."
+section: guide
+order: 20
+---
+# Config
+
+The database block of `config/app.yaml`:
+
+```yaml src=config/app.yaml#db
+db:
+  host: localhost
+  port: 5432
+```
+
+## Settings
+
+> [!WARNING]
+> Keep the port in step with the database server.