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-example-no-output-region/modules/demo/never_test.go

@@ -0,0 +1,11 @@
+package demo_test
+
+func Example_neverRun() {
+	neverRunHelper()
+}
+
+func neverRunHelper() {
+	// docs:start never
+	_ = 1
+	// docs:end never
+}