feat(cbz): adapt reader to real archive structure — PageIndex skips macOS junk (__MACOSX/ and ._ AppleDouble were polluting pages with 163-byte blacks), pages endpoint derives chapters[{title,start}] from folder layout, imageless zip now lands state=error instead of an empty reader, CbzReader gains 目录 sidebar + prev/next chapter (TextReader pattern, rd-* classes); pagesidx cache key bumped for one-time invalidation; e2e on 311MB 調教開關：第二季.zip: 15048→7524 real pages, 52 chapters, all JPEGs

backend/cmd/webui/handlers/content.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"net/http"
 	"os"
+	"path"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -118,7 +119,7 @@ func (h *H) openBook(c *gin.Context, b store.Book, root string) (*os.File, int64
 
 func (h *H) pageIndex(c *gin.Context, b store.Book, root string) ([]string, error) {
 	hash := bookfile.Hash(b.FileSize, b.ModTS)
-	key := fmt.Sprintf("pagesidx:%d:%s", b.ID, hash)
+	key := fmt.Sprintf("pagesidx2:%d:%s", b.ID, hash) // 前缀换代 = 索引逻辑变更时一次性作废旧缓存
 	if v, ok := h.rdb.Get(c, key); ok && v != "" {
 		return strings.Split(v, "\n"), nil
 	}
@@ -158,7 +159,48 @@ func (h *H) PagesCount(c *gin.Context) {
 		err(c, http.StatusUnprocessableEntity, "broken", e.Error())
 		return
 	}
-	c.JSON(http.StatusOK, gin.H{"count": len(idx)})
+	c.JSON(http.StatusOK, gin.H{"count": len(idx), "chapters": chaptersOf(idx)})
+}
+
+type cbzChapter struct {
+	Title string `json:"title"`
+	Start int    `json:"start"`
+}
+
+// chaptersOf 页索引已自然序排列,按父目录分组:每个新目录开一章,标题取目录名;扁平包或只有一组返回 nil
+func chaptersOf(idx []string) []cbzChapter {
+	type grp struct {
+		dir   string
+		start int
+	}
+	var grps []grp
+	last := "\x00"
+	for i, n := range idx {
+		d := path.Dir(n)
+		if d == last {
+			continue
+		}
+		last = d
+		if d == "." { // 根目录散页不开章
+			continue
+		}
+		grps = append(grps, grp{d, i})
+	}
+	if len(grps) < 2 {
+		return nil
+	}
+	titles := make(map[string]int)
+	out := make([]cbzChapter, len(grps))
+	for i, g := range grps {
+		out[i] = cbzChapter{Title: path.Base(g.dir), Start: g.start}
+		titles[out[i].Title]++
+	}
+	for i, g := range grps { // 同名目录(不同父级)撞车 → 用全路径消歧
+		if titles[out[i].Title] > 1 {
+			out[i].Title = g.dir
+		}
+	}
+	return out
 }
 
 func (h *H) Page(c *gin.Context) {

backend/cmd/webui/handlers/content_test.go

@@ -1,6 +1,8 @@
 package handlers_test
 
 import (
+	"archive/zip"
+	"bytes"
 	"context"
 	"encoding/json"
 	"net/http"
@@ -103,6 +105,76 @@ func TestPages(t *testing.T) {
 	}
 }
 
+func zipTo(t *testing.T, path string, kv map[string]string) {
+	t.Helper()
+	os.MkdirAll(filepath.Dir(path), 0o755)
+	buf := &bytes.Buffer{}
+	zw := zip.NewWriter(buf)
+	for n, v := range kv {
+		w, err := zw.Create(n)
+		if err != nil {
+			t.Fatal(err)
+		}
+		w.Write([]byte(v))
+	}
+	zw.Close()
+	os.WriteFile(path, buf.Bytes(), 0o644)
+}
+
+func TestPagesChaptersAndNoImageZip(t *testing.T) {
+	st, sc, h, booksDir := setupAPI(t)
+	tok := adminToken(t, h)
+	lib, root := newLibrary(t, st, h, tok, booksDir, "ch")
+	zipTo(t, filepath.Join(root, "show.cbz"), map[string]string{
+		"第2季/第2話/0001.jpg":     "IMG2",
+		"第2季/第1話/0001.jpg":     "IMG1a",
+		"第2季/第1話/._0001.jpg":   "junk",
+		"__MACOSX/第2季/._0001.jpg": "junk",
+	})
+	zipTo(t, filepath.Join(root, "videos.zip"), map[string]string{"ep/01.mkv": "x"})
+	scanNow(t, sc, lib)
+
+	bookID := func(q string) string {
+		w := do(h, "GET", "/api/books?q="+q, tok, nil)
+		var bs []map[string]any
+		json.Unmarshal(w.Body.Bytes(), &bs)
+		if len(bs) != 1 {
+			t.Fatalf("q=%s books: %s", q, w.Body)
+		}
+		return itoa(bs[0]["id"])
+	}
+	cbzID := bookID("show")
+	w := do(h, "GET", "/api/books/"+cbzID+"/pages", tok, nil)
+	var pg struct {
+		Count    int `json:"count"`
+		Chapters []struct {
+			Title string `json:"title"`
+			Start int    `json:"start"`
+		} `json:"chapters"`
+	}
+	json.Unmarshal(w.Body.Bytes(), &pg)
+	if pg.Count != 2 || len(pg.Chapters) != 2 {
+		t.Fatalf("pages want 2/2ch got %s", w.Body)
+	}
+	if pg.Chapters[0].Title != "第1話" || pg.Chapters[0].Start != 0 || pg.Chapters[1].Start != 1 {
+		t.Fatalf("chapters: %s", w.Body)
+	}
+	ww := do(h, "GET", "/api/books/"+cbzID+"/pages/0", tok, nil)
+	if ww.Code != 200 || ww.Body.String() != "IMG1a" {
+		t.Fatalf("page0 must be real image (junk filtered): %d %s", ww.Code, ww.Body)
+	}
+	if ww := do(h, "GET", "/api/books/"+cbzID+"/pages/2", tok, nil); ww.Code != 404 {
+		t.Fatalf("junk-indexed page must be gone: %d", ww.Code)
+	}
+	// 无图 zip → state=error,而不是空白 reader
+	w = do(h, "GET", "/api/books/"+bookID("videos"), tok, nil)
+	var bk map[string]any
+	json.Unmarshal(w.Body.Bytes(), &bk)
+	if bk["state"] != "error" || !strings.Contains(bk["error"].(string), "no images") {
+		t.Fatalf("empty-image zip want error, got %s", w.Body)
+	}
+}
+
 func TestBrokenCBZ(t *testing.T) {
 	st, sc, h, booksDir := setupAPI(t)
 	atok := adminToken(t, h)