fix: reader loads the full chapter list for prev/next and the dropdown

The reader fetched only the first 200 chapters, so a deep chapter (#250) fell
outside the window and its prev/next chevrons resolved to null — a dead end —
and the chapter dropdown was truncated. Add listAllChapters, which pages
through the API's 200-row cap, and use it in the reader loader.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/lib/api/chapters.test.ts

@@ -9,6 +9,7 @@ import {
 } from 'vitest';
 import {
     listChapters,
+    listAllChapters,
     getChapter,
     getChapterPages,
     createChapter,
@@ -142,6 +143,30 @@ describe('chapters api client', () => {
         });
     });
 
+    it('listAllChapters pages through the 200-row cap and returns every chapter', async () => {
+        const mk = (n: number) => ({ ...chapterFixture, id: `c${n}`, number: n });
+        const first = Array.from({ length: 200 }, (_, i) => mk(i + 1));
+        const second = Array.from({ length: 50 }, (_, i) => mk(i + 201));
+        fetchSpy
+            .mockResolvedValueOnce(ok({ items: first, page: { limit: 200, offset: 0, total: 250 } }))
+            .mockResolvedValueOnce(ok({ items: second, page: { limit: 200, offset: 200, total: 250 } }));
+
+        const all = await listAllChapters('m1');
+        expect(all).toHaveLength(250);
+        expect(all[249].number).toBe(250);
+        expect(fetchSpy.mock.calls[0][0]).toContain('offset=0');
+        expect(fetchSpy.mock.calls[1][0]).toContain('offset=200');
+    });
+
+    it('listAllChapters stops after a short final page (single request)', async () => {
+        fetchSpy.mockResolvedValueOnce(
+            ok({ items: [chapterFixture], page: { limit: 200, offset: 0, total: 1 } })
+        );
+        const all = await listAllChapters('m1');
+        expect(all).toHaveLength(1);
+        expect(fetchSpy).toHaveBeenCalledTimes(1);
+    });
+
     it('getChapterPages unwraps the {pages} envelope into the array', async () => {
         fetchSpy.mockResolvedValueOnce(
             ok({

frontend/src/lib/api/chapters.ts

@@ -40,6 +40,28 @@ export async function listChapters(
     );
 }
 
+/**
+ * Every chapter of a manga, in display order, paging through the API (which
+ * clamps `limit` to 200 per request). The reader needs the complete list so
+ * prev/next navigation and the chapter dropdown work for a deep chapter — a
+ * single 200-row window dead-ended chapter #250 with null neighbours.
+ */
+export async function listAllChapters(mangaId: string): Promise<Chapter[]> {
+    const PAGE = 200;
+    const all: Chapter[] = [];
+    let offset = 0;
+    // Hard iteration cap (200 * 100 = 20k chapters) so a bad `total` can never
+    // spin forever.
+    for (let i = 0; i < 100; i++) {
+        const { items, page } = await listChapters(mangaId, { limit: PAGE, offset });
+        all.push(...items);
+        offset += items.length;
+        const total = page.total ?? all.length;
+        if (items.length < PAGE || all.length >= total) break;
+    }
+    return all;
+}
+
 export async function getChapter(mangaId: string, chapterId: string): Promise<Chapter> {
     return request<Chapter>(
         `/v1/mangas/${encodeURIComponent(mangaId)}/chapters/${encodeURIComponent(chapterId)}`