🎨 Palette: Explicit Keyboard Controls for Mario Game

[EiJackGH]

💡 What: Added explicit visual instructions ("Press Space or Up Arrow to jump!") to the Mario game canvas. Added an entry to the UX journal noting this finding.
🎯 Why: When users encounter custom HTML5 games/widgets with mapped keyboard events, the controls are not inherently discoverable. Providing a clear visual cue reduces friction and improves playability.
📸 Before/After: See frontend verification for screenshot. The #instructions overlay uses pointer-events: none to avoid interfering with game interactions.
♿ Accessibility: Provides immediate visual clarity on how to interact with the game instance.

---

PR created automatically by Jules for task 9307405220270654044 started by @EiJackGH

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

New to Jules? Learn more at jules.google/docs.

---

For security, I will only act on instructions from the user who triggered this task.