test(01-02): add failing test for layered compass config

- Cover six-level precedence, env mapping, .env, Set/Persist/Reload
- Require HasConfig merge before plugin Register
- Assert hello command observes overlay and plugin defaults

party/registry_test.go

@@ -1,8 +1,12 @@
 package party
 
 import (
+	"io/fs"
+	"os"
+	"path/filepath"
 	"strings"
 	"testing"
+	"testing/fstest"
 
 	"git.golem15.com/golem15/summercms/backpack"
 	"git.golem15.com/golem15/summercms/compass"
@@ -27,6 +31,51 @@ func (p *tracePlugin) Boot(*backpack.App) error {
 	return nil
 }
 
+type configPlugin struct {
+	id   string
+	fsys fs.FS
+	got  *int
+}
+
+func (p *configPlugin) ID() string         { return p.id }
+func (p *configPlugin) Requires() []string { return nil }
+func (p *configPlugin) ConfigFS() fs.FS    { return p.fsys }
+
+func (p *configPlugin) Register(app *backpack.App) error {
+	if app != nil && app.Config != nil {
+		*p.got = app.Config.Int("golem15.hello.posts_per_page")
+	}
+	return nil
+}
+
+func (p *configPlugin) Boot(*backpack.App) error { return nil }
+
+func TestActivateMergesHasConfigBeforeRegister(t *testing.T) {
+	dir := t.TempDir()
+	if err := os.WriteFile(filepath.Join(dir, "app.yaml"), []byte("name: app\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	cfg, err := compass.Load(dir)
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	var got int
+	p := &configPlugin{
+		id:  "golem15.hello",
+		got: &got,
+		fsys: fstest.MapFS{
+			"config/config.yaml": {Data: []byte("posts_per_page: 10\n")},
+		},
+	}
+	app := backpack.New(cfg)
+	if _, err := activate([]Plugin{p}, app, []string{"golem15.hello"}); err != nil {
+		t.Fatalf("activate: %v", err)
+	}
+	if got != 10 {
+		t.Fatalf("posts_per_page during Register = %d, want 10 (HasConfig must merge before Register)", got)
+	}
+}
+
 func TestActivateRunsAllRegisterBeforeAnyBoot(t *testing.T) {
 	var log []string
 	hello := &tracePlugin{id: "golem15.hello", log: &log}