fix(summer): pass delegated command flags to the app binary

- delegateCommand builds a Passthrough bonfire command, so
  `summer serve --addr :8123`, `summer serve --help` and `-h` reach the
  app binary instead of failing with "unknown flag: --addr"
- one leading "--" is dropped so `summer serve -- --addr :8123` still
  works
- appRunner is a package-level seam that tests replace to capture argv

cmd/summer/runtime.go

@@ -13,14 +13,23 @@ import (
 	"git.golem15.com/golem15/summercms/modules/bonfire"
 )
 
+// appRunner runs the app binary with argv; tests replace it.
+var appRunner = runAppBinary
+
 func delegateCommand(name, description string) bonfire.Command {
 	return bonfire.Command{
 		Name:        name,
 		Description: description,
+		Passthrough: true,
 		Run: func(ctx context.Context, in bonfire.Input, out bonfire.Output) error {
-			argv := []string{name}
-			argv = append(argv, in.Args()...)
-			return runAppBinary(ctx, argv, out)
+			args := in.Args()
+			// One leading "--" is dropped so the older
+			// `summer serve -- --addr :8123` form keeps working.
+			if len(args) > 0 && args[0] == "--" {
+				args = args[1:]
+			}
+			argv := append([]string{name}, args...)
+			return appRunner(ctx, argv, out)
 		},
 	}
 }