fix(web): show Resume Reading on the manga CTA when the target volume is in progress (#280)

The series hero CTA only inspected chapter.read, so a volume with saved
partial progress (e.g. 18%) still rendered "Start Reading" — the button
contradicted the progress indicator on the same page. The resume target
with progress > 0 now renders "Resume Reading"; untouched series keep
"Start Reading" and mid-series targets keep "Continue".

Fixes #188

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

web/src/pages/ItemDetail/MangaContent.test.tsx

@@ -164,6 +164,32 @@ describe("MangaContent", () => {
     expect(cta).toHaveAttribute("href", "/reader/ebook/v02?libraryId=7" + seriesBackTo);
   });
 
+  // Regression test for issue #188: partial progress on the resume target
+  // must surface as "Resume Reading", not "Start Reading".
+  it("shows a Resume Reading hero CTA when the target volume is partially read", () => {
+    render(
+      <MemoryRouter>
+        <MangaContent
+          item={mangaItem([
+            {
+              content_id: "v01",
+              title: "Railgun v01",
+              chapter_index: 1,
+              volume: "v01",
+              progress: 0.18,
+            },
+            { content_id: "v02", title: "Railgun v02", chapter_index: 2, volume: "v02" },
+          ])}
+          libraryId={7}
+        />
+      </MemoryRouter>,
+    );
+
+    const cta = screen.getByRole("link", { name: /Resume Reading/i });
+    expect(cta).toHaveTextContent("Volume 1");
+    expect(cta).toHaveAttribute("href", "/reader/ebook/v01?libraryId=7" + seriesBackTo);
+  });
+
   it("offers a Read Again CTA from the start once every chapter is read", () => {
     render(
       <MemoryRouter>

web/src/pages/ItemDetail/MangaContent.tsx

@@ -271,8 +271,12 @@ export default function MangaContent({
   const anyRead = chapterRows.some((chapter) => chapter.read === true);
   const resume = useMemo(() => firstUnreadChapter(entries), [entries]);
   const fallbackStart = entries.length > 0 ? flattenFirst(entries) : null;
+  const resumeInProgress = (resume?.chapter.progress ?? 0) > 0;
   const cta = resume
-    ? { ...resume, verb: anyRead ? "Continue" : "Start Reading" }
+    ? {
+        ...resume,
+        verb: resumeInProgress ? "Resume Reading" : anyRead ? "Continue" : "Start Reading",
+      }
     : fallbackStart
       ? { ...fallbackStart, verb: "Read Again" }
       : null;