Add configurable sequence numbering command

tests/contract/sequence_preview_test.go

@@ -0,0 +1,53 @@
+package contract
+
+import (
+	"context"
+	"path/filepath"
+	"testing"
+
+	"github.com/rogeecn/renamer/internal/sequence"
+)
+
+func TestSequencePreviewDefaultNumbering(t *testing.T) {
+	tmp := t.TempDir()
+
+	createFile(t, filepath.Join(tmp, "draft.txt"))
+	createFile(t, filepath.Join(tmp, "notes.txt"))
+	createFile(t, filepath.Join(tmp, "plan.txt"))
+
+	opts := sequence.DefaultOptions()
+	opts.WorkingDir = tmp
+
+	plan, err := sequence.Preview(context.Background(), opts, nil)
+	if err != nil {
+		t.Fatalf("preview error: %v", err)
+	}
+
+	if plan.Summary.TotalCandidates != 3 {
+		t.Fatalf("expected 3 candidates, got %d", plan.Summary.TotalCandidates)
+	}
+	if plan.Summary.RenamedCount != 3 {
+		t.Fatalf("expected 3 renamed entries, got %d", plan.Summary.RenamedCount)
+	}
+
+	expected := []string{"001_draft.txt", "002_notes.txt", "003_plan.txt"}
+	if len(plan.Candidates) != 3 {
+		t.Fatalf("expected 3 planned candidates, got %d", len(plan.Candidates))
+	}
+	for i, candidate := range plan.Candidates {
+		if candidate.ProposedPath != expected[i] {
+			t.Fatalf("candidate %d proposed %s, expected %s", i, candidate.ProposedPath, expected[i])
+		}
+	}
+
+	if plan.Summary.AppliedWidth != 3 {
+		t.Fatalf("expected applied width 3, got %d", plan.Summary.AppliedWidth)
+	}
+
+	if plan.Config.Start != 1 {
+		t.Fatalf("expected start 1, got %d", plan.Config.Start)
+	}
+	if plan.Config.Placement != sequence.PlacementPrefix {
+		t.Fatalf("expected prefix placement, got %s", plan.Config.Placement)
+	}
+}