feat(01-03): add deterministic rich CLI output

- Inject bonfire.Output from stdin/stdout/stderr with stdlib widgets and x/term
- Degrade spinner, progress, table and prompts without a TTY or color
- Reject plugin command names that are not namespace:verb

cmd/summer/main.go

@@ -10,7 +10,11 @@ import (
 )
 
 func main() {
-	root := bonfire.NewRoot("summer", toolCommands(), os.Stdout)
+	root, err := bonfire.NewRoot("summer", toolCommands(), os.Stdout)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
 	root.SetArgs(os.Args[1:])
 	if err := root.Execute(); err != nil {
 		fmt.Fprintln(os.Stderr, err)