Correct engine construction edge cases

internal/filecatalog/catalog_test.go

@@ -54,7 +54,7 @@ func TestFindFSYAMLFilesNestedSortedAndFiltered(t *testing.T) {
 		"other/ignored.yaml":        &fstest.MapFile{Data: []byte("id: ignored")},
 	}
 
-	got, err := FindFSYAMLFiles(context.Background(), fsys, " prompts ")
+	got, err := FindFSYAMLFiles(context.Background(), fsys, "prompts")
 	if err != nil {
 		t.Fatalf("expected no error, got %v", err)
 	}
@@ -98,8 +98,11 @@ func TestCleanFSRoot(t *testing.T) {
 		want string
 	}{
 		{name: "empty", root: "", want: "."},
+		{name: "whitespace only", root: " \t ", want: "."},
 		{name: "dot", root: ".", want: "."},
-		{name: "trimmed", root: " prompts/../profiles ", want: "profiles"},
+		{name: "cleaned", root: "prompts/../profiles", want: "profiles"},
+		{name: "leading whitespace preserved", root: " profiles", want: " profiles"},
+		{name: "trailing whitespace preserved", root: "profiles ", want: "profiles "},
 	}
 
 	for _, tc := range tests {