Initialize narratio Go module and CLI scaffold

internal/logging/doc.go

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+// Package logging provides structured logger construction for narratio.
+package logging

internal/logging/logging.go

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+package logging
+
+import (
+	"io"
+	"log/slog"
+	"os"
+)
+
+// NewLogger creates a text slog logger.
+func NewLogger(out io.Writer, level slog.Level) *slog.Logger {
+	if out == nil {
+		out = os.Stderr
+	}
+
+	handler := slog.NewTextHandler(out, &slog.HandlerOptions{Level: level})
+	return slog.New(handler)
+}

internal/logging/logging_test.go

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+package logging
+
+import (
+	"bytes"
+	"log/slog"
+	"strings"
+	"testing"
+)
+
+func TestNewLoggerWritesOutput(t *testing.T) {
+	var buf bytes.Buffer
+	logger := NewLogger(&buf, slog.LevelInfo)
+
+	if logger == nil {
+		t.Fatal("logger is nil")
+	}
+
+	logger.Info("hello", "component", "test")
+	out := buf.String()
+	if !strings.Contains(out, "hello") {
+		t.Fatalf("output = %q, want to contain message", out)
+	}
+}
+
+func TestNewLoggerNilWriter(t *testing.T) {
+	logger := NewLogger(nil, slog.LevelInfo)
+	if logger == nil {
+		t.Fatal("logger is nil")
+	}
+	logger.Info("should not panic")
+}