(new): JSON HTML escaping control

- add Formatter.JSONEscapeHTML and SetJSONEscapeHTML to let JSON writers preserve HTML-sensitive characters when needed while keeping escaping enabled by default.
- switch JSON output to json.Encoder, preserve existing Print/Println newline semantics, and cover the new escaping behavior in tests.

logger_test.go

@@ -342,6 +342,42 @@ func TestJsonWriterPrintAllowsEmptyMessages(t *testing.T) {
 	}
 }
 
+func TestJsonWriterPrintDoesNotAppendNewline(t *testing.T) {
+	var buf bytes.Buffer
+	writer := CreateJsonWriter(&buf, false)
+
+	if err := writer.Print(INFO, "TEST", nil, "hello"); err != nil {
+		t.Fatalf("Print() error = %v", err)
+	}
+
+	if bytes.HasSuffix(buf.Bytes(), []byte("\n")) {
+		t.Fatalf("Print() should not append newline, got %q", buf.String())
+	}
+}
+
+func TestJsonWriterSetJSONEscapeHTML(t *testing.T) {
+	var escaped bytes.Buffer
+	escapedWriter := CreateJsonWriter(&escaped, false)
+
+	if err := escapedWriter.Print(INFO, "TEST", nil, "<>&"); err != nil {
+		t.Fatalf("Print() with default formatter error = %v", err)
+	}
+	if strings.Contains(escaped.String(), "<>&") {
+		t.Fatalf("default JSON output should escape HTML-sensitive characters, got %q", escaped.String())
+	}
+
+	var raw bytes.Buffer
+	rawWriter := CreateJsonWriter(&raw, false).
+		SetFormatter(NewFormatter().SetFormat("%m").SetJSONEscapeHTML(false))
+
+	if err := rawWriter.Print(INFO, "TEST", nil, "<>&"); err != nil {
+		t.Fatalf("Print() with SetJSONEscapeHTML(false) error = %v", err)
+	}
+	if !strings.Contains(raw.String(), "<>&") {
+		t.Fatalf("SetJSONEscapeHTML(false) should preserve HTML-sensitive characters, got %q", raw.String())
+	}
+}
+
 func TestJsonWriterPrintPreservesTrailingNewlineSemantic(t *testing.T) {
 	var buf bytes.Buffer
 	writer := CreateJsonWriter(&buf, false)
@@ -354,6 +390,9 @@ func TestJsonWriterPrintPreservesTrailingNewlineSemantic(t *testing.T) {
 	if !bytes.HasSuffix(data, []byte("\n")) {
 		t.Fatalf("JSON output should end with newline, got %q", data)
 	}
+	if bytes.HasSuffix(bytes.TrimSuffix(data, []byte("\n")), []byte("\n")) {
+		t.Fatalf("JSON output should end with exactly one newline, got %q", data)
+	}
 
 	var message LoggerJsonMessage
 	if err := json.Unmarshal(bytes.TrimSuffix(data, []byte("\n")), &message); err != nil {