feat: Add a Speaker Mode (Presenter Mode) with cloud-based multi-device real-time interaction

[fyn93]

Why

bento/slides already ships a lightweight presenter window, but for real-world scenarios — conferences, classrooms, online meetings — a full-featured speaker mode is the missing piece. Since slides are rendered as pure HTML in the browser, adding one is highly feasible and would give the deck a significant usability boost.

What

1. Speaker mode for HTML-based slides
A dedicated presenter view on top of bento/slides, including:

• Current slide + next-slide preview
• Speaker notes (if any) and elapsed-time timer
• Slide thumbnails / overview navigation
• Optional laser-pointer & drawing overlay on the audience screen

2. Cloud-native hosting via CNB (cnb.cool)
cnb.cool is Tencent's next-generation R&D toolchain. It can run the PPT app directly in the cloud, so a deck is always reachable by URL — no local file distribution or installation required.

3. Real-time multi-device interaction over WebSocket
Because the app runs in the cloud, it's natural to keep a persistent socket connection between the presenter and all viewers:

• Audience view — follows the presenter's slide changes in real time
• Speaker view — drives the deck and sees audience reactions (e.g., raised hands, emoji)
• Phone remote control — scan a QR code to control slides (next / prev / jump) from a phone
• Tablet / pad whiteboard — touch drawing & annotation that syncs back to the audience screen

Expected value

• One shareable URL, zero installation
• Presenter and audience always in sync, no extra screen-sharing software needed
• Mobile and tablet become first-class input devices instead of afterthoughts

Reference

• Live demo: https://cnb.cool/Black_Myth_wukong/next-ppt

[nyblnet]

Thanks for the suggestion. This is similar to #283? Maybe we can do something this weekend on this.

[thiswillbeyourgithub]

Related to #543

[TrueBeastEmperor]

The speaker mode idea is great. It'd be nice for it to me improved upon a bit.

[nyblnet]

Thanks for the input here. Currently speaker mode is really only focused on shared decks, but sending a file around has it's drawbacks and convenience is a big one. This require rethinking a bit of the infrastructure but also the core philosophy of Bento. Will try working on this in the next few days.