fix: speed up reveal animations and update demo video sources

[hoangsonww]

This pull request focuses on improving the user experience of reveal animations and demo videos on the site. The main changes include making reveal animations much faster and more responsive, as well as switching demo videos to use externally hosted links for better reliability.

Reveal animation improvements:

• Reduced reveal animation durations and delays in wiki/styles.css and wiki/app.js to make UI elements appear faster and feel more responsive. This includes halving the animation times, decreasing blur and translation distances, and reducing the delay between items in grids and bars. [1] [2] [3]
• Adjusted the IntersectionObserver in wiki/app.js to trigger reveals earlier—now elements begin animating as soon as any part enters the viewport, and a 240px band above the fold is pre-revealed to ensure smoother transitions as users scroll.

Demo video hosting:

• Updated the video sources in index.html to use externally hosted URLs on GitHub instead of local images/*.mp4 files, which should improve loading reliability and reduce repository size.

[gemini-code-assist]

Code Review

This pull request updates video sources in index.html to external URLs and optimizes the reveal animations in wiki/app.js and wiki/styles.css by reducing durations and adjusting trigger thresholds for a snappier user experience. Review feedback identifies that the new video URLs in index.html contain unintended newline characters which could break playback, and suggests consolidating them onto single lines.

[gemini-code-assist]

The video src URL is split across two lines, which introduces a newline character into the attribute value. This can lead to broken video playback or unexpected behavior in some browsers. The URL and the closing quote should be on the same line.

Suggested change

	<video src="https://github.com/user-attachments/assets/eb592bbf-62a1-4d74-a540-7e066ebe56a4
	" poster="images/repl.png" controls muted playsinline preload="metadata"
	<video src="https://github.com/user-attachments/assets/eb592bbf-62a1-4d74-a540-7e066ebe56a4" poster="images/repl.png" controls muted playsinline preload="metadata"

[gemini-code-assist]

The video src URL is split across two lines, which introduces a newline character into the attribute value. This can lead to broken video playback or unexpected behavior in some browsers. The URL and the closing quote should be on the same line.

Suggested change

	<video src="https://github.com/user-attachments/assets/bc3b3204-fd87-436f-9467-604535edb4e2
	" poster="images/cli.png" controls muted playsinline preload="metadata"
	<video src="https://github.com/user-attachments/assets/bc3b3204-fd87-436f-9467-604535edb4e2" poster="images/cli.png" controls muted playsinline preload="metadata"

[gemini-code-assist]

The video src URL is split across two lines, which introduces a newline character into the attribute value. This can lead to broken video playback or unexpected behavior in some browsers. The URL and the closing quote should be on the same line.

Suggested change

	<video src="https://github.com/user-attachments/assets/218cd64f-40fe-4836-9c62-c7a08538056b
	" poster="images/ui.png" controls muted playsinline preload="metadata"
	<video src="https://github.com/user-attachments/assets/218cd64f-40fe-4836-9c62-c7a08538056b" poster="images/ui.png" controls muted playsinline preload="metadata"