feat(11.1-01): verify src= code blocks and add summer docs:sync

- src= fences name a file, a Go declaration or Example body, or a docs:start region
- confinement: relative clean paths inside the root, no dotfiles or .env,
  no nested go.mod modules, Examples need // Output:, test regions must run
- a drifted or missing snippet is a problem, so docs:build writes nothing
- docs:sync rewrites drifted fence bodies in place
- fences render in figure.code with a source caption; .md fences keep only the language
- bonfire ExampleCall is the first verified example, shown in setup/installation

cmd/summer/main.go

@@ -47,6 +47,7 @@ func toolCommands() []bonfire.Command {
 		delegateScheduleRunCommand(),
 		delegateCommand("queue:clear", "Clear pending queued jobs in the app binary"),
 		docsBuildCommand(),
+		docsSyncCommand(),
 	}
 }