Add configurable sequence numbering command

tests/integration/sequence_prefix_test.go

@@ -0,0 +1,53 @@
+package integration
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/rogeecn/renamer/internal/history"
+	"github.com/rogeecn/renamer/internal/sequence"
+)
+
+func TestSequenceApplyWithNumberPrefix(t *testing.T) {
+	tmp := t.TempDir()
+
+	createIntegrationFile(t, filepath.Join(tmp, "cover.png"))
+	createIntegrationFile(t, filepath.Join(tmp, "index.png"))
+
+	opts := sequence.DefaultOptions()
+	opts.WorkingDir = tmp
+	opts.Placement = sequence.PlacementPrefix
+	opts.Separator = "-"
+	opts.NumberPrefix = "seq"
+
+	plan, err := sequence.Preview(context.Background(), opts, nil)
+	if err != nil {
+		t.Fatalf("preview error: %v", err)
+	}
+
+	entry, err := sequence.Apply(context.Background(), opts, plan)
+	if err != nil {
+		t.Fatalf("apply error: %v", err)
+	}
+
+	if _, err := os.Stat(filepath.Join(tmp, "seq001-cover.png")); err != nil {
+		t.Fatalf("expected renamed file exists: %v", err)
+	}
+	if _, err := os.Stat(filepath.Join(tmp, "seq002-index.png")); err != nil {
+		t.Fatalf("expected renamed file exists: %v", err)
+	}
+
+	meta, ok := entry.Metadata["sequence"].(map[string]any)
+	if !ok {
+		t.Fatalf("sequence metadata missing")
+	}
+	if prefix, ok := meta["prefix"].(string); !ok || prefix != "seq" {
+		t.Fatalf("expected metadata prefix 'seq', got %#v", meta["prefix"])
+	}
+
+	if _, err := history.Undo(tmp); err != nil {
+		t.Fatalf("undo error: %v", err)
+	}
+}