(refactor): prepare breaking v2 API

- rename package to sneklog and move module to /v2
- replace text output flags with writer formatters
- remove external color dependencies
- update migration notes and coverage

logger_test.go

@@ -1,4 +1,4 @@
-package slog
+package sneklog
 
 import (
 	"bytes"
@@ -17,6 +17,9 @@ type stubLoggerWriter struct {
 	messages   []any
 }
 
+func (w *stubLoggerWriter) Formatter() *Formatter {
+	return &Formatter{}
+}
 func (w *stubLoggerWriter) Close() error {
 	w.closeCalls++
 	return w.closeErr
@@ -98,7 +101,7 @@ func TestLoggerPreservesMessageTypesWithoutReplacers(t *testing.T) {
 }
 
 func TestCreateTextWriterCloseOnNonCloserIsNoOp(t *testing.T) {
-	writer := CreateTextWriter(&bytes.Buffer{}, false, false)
+	writer := CreateTextWriter(&bytes.Buffer{})
 	if err := writer.Close(); err != nil {
 		t.Fatalf("Close() error = %v", err)
 	}
@@ -113,7 +116,7 @@ func TestCreateTextWriterDoesNotCloseExternalCloser(t *testing.T) {
 		_ = file.Close()
 	})
 
-	writer := CreateTextWriter(file, false, false)
+	writer := CreateTextWriter(file)
 	if err := writer.Close(); err != nil {
 		t.Fatalf("Close() error = %v", err)
 	}
@@ -186,10 +189,72 @@ func TestJsonWriterPrintPreservesTrailingNewlineSemantic(t *testing.T) {
 	}
 }
 
+func TestFormatterHandlesEmptyTracebackPlaceholders(t *testing.T) {
+	formatter := NewFormatter().
+		SetFormat("%m|%b|%B|%M|%f|%n|%s|%p")
+
+	got := formatter.FormatMessage(INFO, "TEST", nil, "hello")
+	if got != "hello|||||||" {
+		t.Fatalf("empty traceback placeholders should be empty, got %q", got)
+	}
+}
+
+func TestFormatterDoesNotInterpretPlaceholdersInsideMessages(t *testing.T) {
+	formatter := NewFormatter().
+		SetFormat("%L:%m")
+
+	message := "literal %L %s %p"
+	got := formatter.FormatMessage(INFO, "TEST", nil, message)
+	if got != "INFO:literal %L %s %p" {
+		t.Fatalf("message placeholder-looking text should stay literal, got %q", got)
+	}
+}
+
+func TestNewFormatterDoesNotMutateDefaultFormatter(t *testing.T) {
+	formatter := NewFormatter()
+	formatter.SetFormat("custom")
+
+	if DefaultTextFormatter.Format == "custom" {
+		t.Fatal("NewFormatter() should return a copy, not mutate DefaultTextFormatter")
+	}
+}
+
+func TestTextWriterColorOutputHonorsColorOnlyStdoutFalse(t *testing.T) {
+	var buf bytes.Buffer
+	formatter := NewFormatter().
+		SetFormat("%m").
+		SetColorOutput(true).
+		SetColorOnlyStdout(false)
+	writer := CreateTextWriter(&buf).SetFormatter(formatter)
+
+	if err := writer.Print(INFO, "TEST", nil, "hello"); err != nil {
+		t.Fatalf("Print() error = %v", err)
+	}
+	if !strings.Contains(buf.String(), "\x1b[") {
+		t.Fatalf("ColorOnlyStdout(false) should allow color for external writers, got %q", buf.String())
+	}
+}
+
+func TestTextWriterColorOutputCanBeDisabled(t *testing.T) {
+	var buf bytes.Buffer
+	formatter := NewFormatter().
+		SetFormat("%m").
+		SetColorOutput(false).
+		SetColorOnlyStdout(false)
+	writer := CreateTextWriter(&buf).SetFormatter(formatter)
+
+	if err := writer.Print(INFO, "TEST", nil, "hello"); err != nil {
+		t.Fatalf("Print() error = %v", err)
+	}
+	if strings.Contains(buf.String(), "\x1b[") {
+		t.Fatalf("SetColorOutput(false) should disable color output, got %q", buf.String())
+	}
+}
+
 func TestCreateTextStdoutWriterDoesNotCloseStdout(t *testing.T) {
 	stdoutFile := swapStdout(t)
 
-	writer := CreateTextStdoutWriter(false, false)
+	writer := CreateTextStdoutWriter()
 	if err := writer.Close(); err != nil {
 		t.Fatalf("Close() error = %v", err)
 	}