feat(01-03): add summer dev watch rebuild loop

- Watch app sources with fsnotify, debounce, and one serialized build.App
- Restart the child only after a successful build and print rebuild latency
- Ignore generated app files and reap the child on cancellation

cmd/summer/main.go

@@ -7,6 +7,7 @@ import (
 
 	"git.golem15.com/golem15/summercms/bonfire"
 	"git.golem15.com/golem15/summercms/internal/build"
+	"git.golem15.com/golem15/summercms/internal/dev"
 )
 
 func main() {
@@ -27,6 +28,7 @@ func toolCommands() []bonfire.Command {
 		buildCommand(),
 		makePluginCommand(),
 		addPluginCommand(),
+		devCommand(),
 	}
 }
 
@@ -72,6 +74,20 @@ func makePluginCommand() bonfire.Command {
 	}
 }
 
+func devCommand() bonfire.Command {
+	return bonfire.Command{
+		Name:        "dev",
+		Description: "Watch sources and rebuild the app binary",
+		Run: func(ctx context.Context, in bonfire.Input, out bonfire.Output) error {
+			dir, err := os.Getwd()
+			if err != nil {
+				return err
+			}
+			return dev.Watch(ctx, dir, out)
+		},
+	}
+}
+
 func addPluginCommand() bonfire.Command {
 	return bonfire.Command{
 		Name:        "plugin:add",