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

modules/bonfire/example_test.go

@@ -0,0 +1,27 @@
+package bonfire_test
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"git.golem15.com/golem15/summercms/modules/bonfire"
+)
+
+func ExampleCall() {
+	commands := []bonfire.Command{{
+		Name:        "acme:greet",
+		Description: "Greet someone by name",
+		Args:        []bonfire.Arg{{Name: "name", Required: true}},
+		Run: func(ctx context.Context, in bonfire.Input, out bonfire.Output) error {
+			name, _ := in.Argument("name")
+			out.Printf("Hello, %s\n", name)
+			return nil
+		},
+	}}
+
+	if err := bonfire.Call(context.Background(), commands, "acme:greet", []string{"blog"}, os.Stdout); err != nil {
+		fmt.Println(err)
+	}
+	// Output: Hello, blog
+}