fix: extract title from h1 or URL slug when page title starts with #

When readallcomics.com pages have a <title> containing only the issue
number (e.g. '#018 (2026)'), fall back to the h1 element first, then
derive the title from the URL slug by stripping the trailing year and
title-casing the hyphen-separated segments.

Closes #4

comic/archive_test.go

@@ -0,0 +1,110 @@
+package comic
+
+import (
+	"archive/zip"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestArchiveError(t *testing.T) {
+	err := ArchiveError{Message: "archive failed", Code: 1}
+	if err.Error() != "archive failed" {
+		t.Errorf("Error() = %q, want %q", err.Error(), "archive failed")
+	}
+}
+
+func TestArchive(t *testing.T) {
+	t.Run("creates cbz with image files", func(t *testing.T) {
+		tmpDir := t.TempDir()
+		title := "TestComic"
+		comicDir := filepath.Join(tmpDir, title)
+		os.MkdirAll(comicDir, os.ModePerm)
+
+		// Create fake image files
+		for _, name := range []string{"TestComic 001.jpg", "TestComic 002.jpg", "TestComic 003.png"} {
+			os.WriteFile(filepath.Join(comicDir, name), []byte("fake image"), 0644)
+		}
+
+		c := &Comic{
+			Title:       title,
+			LibraryPath: tmpDir,
+		}
+
+		err := c.Archive()
+		if err != nil {
+			t.Fatalf("Archive() unexpected error: %v", err)
+		}
+
+		archivePath := filepath.Join(comicDir, title+".cbz")
+		if _, err := os.Stat(archivePath); os.IsNotExist(err) {
+			t.Fatalf("expected archive %s to exist", archivePath)
+		}
+
+		// Verify the zip contains the image files
+		reader, err := zip.OpenReader(archivePath)
+		if err != nil {
+			t.Fatalf("failed to open archive: %v", err)
+		}
+		defer reader.Close()
+
+		if len(reader.File) != 3 {
+			t.Errorf("archive contains %d files, want 3", len(reader.File))
+		}
+	})
+
+	t.Run("excludes non-image files from archive", func(t *testing.T) {
+		tmpDir := t.TempDir()
+		title := "TestComic"
+		comicDir := filepath.Join(tmpDir, title)
+		os.MkdirAll(comicDir, os.ModePerm)
+
+		// Create mixed files
+		os.WriteFile(filepath.Join(comicDir, "page-001.jpg"), []byte("image"), 0644)
+		os.WriteFile(filepath.Join(comicDir, "readme.txt"), []byte("text"), 0644)
+		os.WriteFile(filepath.Join(comicDir, "data.json"), []byte("json"), 0644)
+
+		c := &Comic{
+			Title:       title,
+			LibraryPath: tmpDir,
+		}
+
+		err := c.Archive()
+		if err != nil {
+			t.Fatalf("Archive() unexpected error: %v", err)
+		}
+
+		archivePath := filepath.Join(comicDir, title+".cbz")
+		reader, err := zip.OpenReader(archivePath)
+		if err != nil {
+			t.Fatalf("failed to open archive: %v", err)
+		}
+		defer reader.Close()
+
+		if len(reader.File) != 1 {
+			t.Errorf("archive contains %d files, want 1 (only .jpg)", len(reader.File))
+		}
+	})
+
+	t.Run("handles empty directory", func(t *testing.T) {
+		tmpDir := t.TempDir()
+		title := "EmptyComic"
+		comicDir := filepath.Join(tmpDir, title)
+		os.MkdirAll(comicDir, os.ModePerm)
+
+		c := &Comic{
+			Title:       title,
+			LibraryPath: tmpDir,
+		}
+
+		err := c.Archive()
+		if err != nil {
+			t.Fatalf("Archive() unexpected error: %v", err)
+		}
+
+		archivePath := filepath.Join(comicDir, title+".cbz")
+		if _, err := os.Stat(archivePath); os.IsNotExist(err) {
+			t.Fatalf("expected archive %s to exist even if empty", archivePath)
+		}
+	})
+}