fix(player): keep Next available for the final slide's reveals (#6233)

docs/guides/slideshow.mdx

@@ -63,6 +63,9 @@ Attach the source notes, document, page, or existing deck. Name the audience and
 
 The main story should still make sense when no optional branch is opened.
 
+Use **Next** to step through fragment reveals, including those on the final slide.
+The Next button disappears once the final slide's last reveal is shown.
+
 ## Review it as a presenter
 
 - Each slide makes one clear point.

packages/player/src/slideshow/SlideshowController.ts

@@ -71,7 +71,8 @@ export class SlideshowController {
   }
 
   get canNext(): boolean {
-    // next has a destination: a later slide in this sequence, OR (in a branch) the parent.
+    const slide = this.currentSlide;
+    if (slide && this.frame.fragmentIndex + 1 < slide.fragments.length) return true;
     const slides = this.slidesOf(this.frame.sequenceId);
     return this.frame.slideIndex + 1 < slides.length || this.stack.length > 1;
   }

packages/player/src/slideshow/hyperframes-slideshow.test.ts

@@ -4,8 +4,10 @@ import { handleRuntimeMessage } from "../runtime-message-handler.js";
 import {
   childrenMayStillArrive,
   dropInvalidSlides,
+  HyperframesSlideshow,
   locateSlideshowParts,
 } from "./hyperframes-slideshow.js";
+import { SlideshowController } from "./SlideshowController.js";
 import { slideshowChannelName } from "./slideshowPresenter.js";
 
 // Dynamic import defers custom-element registration until happy-dom is active.
@@ -131,6 +133,44 @@ describe("<hyperframes-slideshow>", () => {
     el.remove();
   });
 
+  it("keeps Next available until the final slide's fragments are revealed", () => {
+    const player = {
+      currentTime: 0,
+      seek: (time: number) => {
+        player.currentTime = time;
+      },
+      play: vi.fn(),
+      pause: vi.fn(),
+      onTimeUpdate: () => () => {},
+    };
+    const controller = new SlideshowController(player, {
+      slides: [
+        { sceneId: "intro", start: 0, end: 5, fragments: [], hotspots: [] },
+        { sceneId: "closing", start: 5, end: 10, fragments: [6, 8, 9], hotspots: [] },
+      ],
+      sequences: {},
+    });
+    const el = new HyperframesSlideshow();
+    document.body.appendChild(el);
+    el.__setControllerForTest(controller);
+
+    try {
+      controller.goToSlide(1);
+      expect(player.currentTime).toBe(6);
+      expect(el.querySelector("[data-hf-next]")).not.toBeNull();
+
+      el.querySelector<HTMLButtonElement>("[data-hf-next]")?.click();
+      expect(player.currentTime).toBe(8);
+      expect(el.querySelector("[data-hf-next]")).not.toBeNull();
+
+      el.querySelector<HTMLButtonElement>("[data-hf-next]")?.click();
+      expect(player.currentTime).toBe(9);
+      expect(el.querySelector("[data-hf-next]")).toBeNull();
+    } finally {
+      el.remove();
+    }
+  });
+
   it("renders an icon-only present button inside the nav cluster in normal mode", () => {
     const el = makeEl({ index: 1, total: 3 });
     const cluster = el.querySelector("[data-hf-nav-cluster]");