fix: keep the theme suite honest on a Windows runner

internal/themes/themes.go

@@ -239,13 +239,24 @@ func (s *Service) Remove(id string) error {
 }
 
 func (s *Service) customThemes() ([]Theme, error) {
-	entries, err := os.ReadDir(s.dir)
+	// Stat before reading: a file sitting where the themes directory belongs
+	// makes ReadDir report not-exist on Windows, which the "nothing imported
+	// yet" branch below would swallow into an empty list on that OS and an
+	// error everywhere else.
+	info, err := os.Stat(s.dir)
 	if os.IsNotExist(err) {
 		return nil, nil
 	}
 	if err != nil {
 		return nil, fmt.Errorf("read themes dir: %w", err)
 	}
+	if !info.IsDir() {
+		return nil, fmt.Errorf("themes path is not a directory: %s", s.dir)
+	}
+	entries, err := os.ReadDir(s.dir)
+	if err != nil {
+		return nil, fmt.Errorf("read themes dir: %w", err)
+	}
 	themes := make([]Theme, 0, len(entries))
 	for _, entry := range entries {
 		if entry.IsDir() || filepath.Ext(entry.Name()) != ".json" {

internal/themes/themes_test.go

@@ -577,14 +577,36 @@ func TestImportRejectsWindowsDeviceNames(t *testing.T) {
 	}
 }
 
+// \r? because the repo pins no .gitattributes, so a Windows checkout hands this
+// test CRLF and a bare \n matches nothing there.
+var docJSONBlock = regexp.MustCompile("(?s)```json\r?\n(.*?)```")
+
+func TestDocJSONBlockReadsBothLineEndings(t *testing.T) {
+	for _, tt := range []struct{ name, newline string }{
+		{name: "lf", newline: "\n"},
+		{name: "crlf", newline: "\r\n"},
+	} {
+		t.Run(tt.name, func(t *testing.T) {
+			doc := "text" + tt.newline + "```json" + tt.newline + "{}" + tt.newline + "```"
+			block := docJSONBlock.FindStringSubmatch(doc)
+			if block == nil {
+				t.Fatalf("no JSON block found in a %s document", tt.name)
+			}
+			if strings.TrimSpace(block[1]) != "{}" {
+				t.Fatalf("block = %q, want the JSON body", block[1])
+			}
+		})
+	}
+}
+
 // The documented example is the shape users copy from, so it answers to the
 // validator like any other imported theme.
 func TestDocumentedExampleIsImportable(t *testing.T) {
 	data, err := os.ReadFile(filepath.Join("..", "..", "docs", "themes.md"))
 	if err != nil {
 		t.Fatalf("read docs/themes.md: %v", err)
 	}
-	block := regexp.MustCompile("(?s)```json\n(.*?)```").FindSubmatch(data)
+	block := docJSONBlock.FindSubmatch(data)
 	if block == nil {
 		t.Fatal("docs/themes.md has no JSON example")
 	}