test(04-04): close translation lookup and catalog boundary coverage

- Cover nested groups, malformed paths, invalid pipes, and compass locale
- Name plugin, file, and key on activation catalog failures
- Prove hello activation reads the translator through towel.WithLocale

Co-authored-by: Cursor <cursoragent@cursor.com>

phrasebook/translator_test.go

@@ -5,6 +5,8 @@ import (
 	"context"
 	"io/fs"
 	"log/slog"
+	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 	"testing/fstest"
@@ -249,3 +251,95 @@ func TestLocaleFallbackSmoke(t *testing.T) {
 		t.Fatalf("production lookup must be silent, got %q", buf.String())
 	}
 }
+
+func TestCatalogBoundaries(t *testing.T) {
+	t.Parallel()
+
+	t.Run("invalid yaml names plugin and file", func(t *testing.T) {
+		err := NewCatalog().Load("golem15.hello", fstest.MapFS{
+			"lang/en/lang.yaml": {Data: []byte("greeting: [\n")},
+		})
+		if err == nil || !strings.Contains(err.Error(), "golem15.hello") || !strings.Contains(err.Error(), "lang/en/lang.yaml") {
+			t.Fatalf("parse error = %v", err)
+		}
+	})
+	t.Run("nested group file flattens under group name", func(t *testing.T) {
+		cat := NewCatalog()
+		err := cat.Load("golem15.hello", fstest.MapFS{
+			"lang/en/validation.yaml": {Data: []byte("fields:\n  name: Name is required\n")},
+		})
+		if err != nil {
+			t.Fatal(err)
+		}
+		tr := NewTranslator(cat, Options{})
+		if got := tr.GetIn("en", "golem15.hello::validation.fields.name", nil); got != "Name is required" {
+			t.Fatalf("nested group = %q", got)
+		}
+	})
+	t.Run("path extra segments and wrong suffix are malformed", func(t *testing.T) {
+		for _, file := range []string{"lang/en/nested/lang.yaml", "lang/en/lang.yml", "i18n/en/lang.yaml"} {
+			err := NewCatalog().Load("golem15.hello", fstest.MapFS{
+				file: {Data: []byte("greeting: Hi\n")},
+			})
+			if err == nil || !strings.Contains(err.Error(), "golem15.hello") || !strings.Contains(err.Error(), "malformed path") {
+				t.Fatalf("%s error = %v", file, err)
+			}
+		}
+	})
+	t.Run("inverted bracket range", func(t *testing.T) {
+		err := NewCatalog().Load("golem15.hello", fstest.MapFS{
+			"lang/en/lang.yaml": {Data: []byte("items: \"[5,2] nope|{1} one\"\n")},
+		})
+		if err == nil || !strings.Contains(err.Error(), "golem15.hello") || !strings.Contains(err.Error(), "lang/en/lang.yaml") || !strings.Contains(err.Error(), "malformed pipe") {
+			t.Fatalf("inverted range error = %v", err)
+		}
+	})
+	t.Run("empty pipe form", func(t *testing.T) {
+		err := NewCatalog().Load("golem15.hello", fstest.MapFS{
+			"lang/en/lang.yaml": {Data: []byte("items: \"one||other\"\n")},
+		})
+		if err == nil || !strings.Contains(err.Error(), "malformed pipe") {
+			t.Fatalf("empty form error = %v", err)
+		}
+	})
+	t.Run("get substitutes name case variants", func(t *testing.T) {
+		cat := NewCatalog()
+		if err := cat.Load("golem15.hello", fstest.MapFS{
+			"lang/en/lang.yaml": {Data: []byte("helloName: \"hi :name :Name :NAME\"\n")},
+		}); err != nil {
+			t.Fatal(err)
+		}
+		tr := NewTranslator(cat, Options{})
+		if got := tr.GetIn("en", "golem15.hello::lang.helloName", map[string]string{"name": "alice"}); got != "hi alice Alice ALICE" {
+			t.Fatalf("Get params = %q", got)
+		}
+	})
+	t.Run("configured locale and fallback", func(t *testing.T) {
+		dir := t.TempDir()
+		if err := os.WriteFile(filepath.Join(dir, "app.yaml"), []byte("locale: pl\nfallback_locale: en\n"), 0o644); err != nil {
+			t.Fatal(err)
+		}
+		cfg, err := compass.Load(dir)
+		if err != nil {
+			t.Fatal(err)
+		}
+		app := backpack.New(cfg)
+		p := &langPlugin{id: "golem15.hello", fsys: fstest.MapFS{
+			"lang/en/lang.yaml": {Data: []byte("greeting: Hello\nonlyEn: English only\n")},
+			"lang/pl/lang.yaml": {Data: []byte("greeting: Cześć\n")},
+		}}
+		if err := Activate(app, []*langPlugin{p}); err != nil {
+			t.Fatal(err)
+		}
+		tr, ok := app.Lookup[*Translator]()
+		if !ok {
+			t.Fatal("translator not published")
+		}
+		if got := tr.Get(context.Background(), "golem15.hello::lang.greeting", nil); got != "Cześć" {
+			t.Fatalf("configured app.locale = %q", got)
+		}
+		if got := tr.GetIn("pl", "golem15.hello::lang.onlyEn", nil); got != "English only" {
+			t.Fatalf("configured fallback = %q", got)
+		}
+	})
+}