feat(01-02): implement layered compass config

- Merge plugin defaults, sorted YAML, SUMMER_ env, overrides and Set
- Persist atomically to env overrides; Reload clears runtime Set
- Discover HasConfig before Register and print layered hello values

examples/hello/plugins/greeter/plugin.go

@@ -29,10 +29,14 @@ func (p *Plugin) Commands() []bonfire.Command {
 		Description: "Print the configured application name",
 		Run: func(ctx context.Context, in bonfire.Input, out bonfire.Output) error {
 			name := ""
+			posts := 0
+			debug := false
 			if p.app != nil && p.app.Config != nil {
 				name = p.app.Config.String("app.name")
+				posts = p.app.Config.Int("golem15.hello.posts_per_page")
+				debug = p.app.Config.Bool("app.debug")
 			}
-			out.Println(name)
+			out.Printf("name=%s posts_per_page=%d debug=%t\n", name, posts, debug)
 			return nil
 		},
 	}}