test(11.1-07): planted fixtures and unit tests for fence, execution and name-form holes

- eighteen violation plants pin nested src=, Go aliases, unrun examples, build membership and command forms
- unit tests cover fence collection, captions, goLang, go doc -c, commandWord and Sync

internal/docsite/testdata/violations/snippet-readme-src/modules/demo/README.md

@@ -0,0 +1,24 @@
+# demo
+
+Demo greets people by name.
+
+```go
+import "example.com/docfixture/modules/demo"
+```
+
+## Usage
+
+Call `demo.Hello` or build a `demo.Greeter` and call `demo.Greeter.Greet`.
+
+See the [start guide](../../docs/guide/start.md#install).
+
+## Testing
+
+```sh
+go test ./modules/demo
+```
+
+```go src=modules/demo/example_test.go#ExampleHello
+fmt.Println(demo.Hello("blog"))
+// Output: Hello, blog
+```

internal/docsite/testdata/violations/snippet-readme-src/want.txt

@@ -0,0 +1,3 @@
+rule: snippet
+file: modules/demo/README.md
+message: modules/demo/example_test.go#ExampleHello: module README code blocks are rendered as written