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

docs/setup/installation.md

@@ -33,3 +33,27 @@ go test -short ./...
 ```
 
 `go test -short` skips the tests that need Docker. Run `go test ./...` without `-short` when Docker is available.
+
+## Check your install
+
+Console commands in SummerCMS are plain `bonfire.Command` values: a name in `namespace:verb` form, its arguments and flags, and a run function that reads input and writes output. The `summer` tool and every application binary are built from such values, and `bonfire.Call` runs one in-process, which is how tests call commands. This example comes from the framework's own tests, so it compiles and runs whenever you run `go test ./...`:
+
+```go src=modules/bonfire/example_test.go#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
+```
+
+If the tests above pass, this example ran and printed `Hello, blog`. See the [bonfire](../../modules/bonfire/README.md) reference for flags, prompts and styled output.