Add simple interactive button demo

[ylee-figma]

Summary

Adds a self-contained index.html page with a simple interactive button. Clicking the button increments and displays a live click counter.

Details

• Single-file, no dependencies or build step required — just open index.html in a browser.
• Modern, responsive card layout with hover/active button states.
• Vanilla JS click handler updates the counter text with correct singular/plural wording.

Walkthrough

simple_button_click_demo.mp4

Button increments the counter on each click.

Initial state
After 4 clicks

Testing

Manually verified in Chrome: page renders and the counter updates correctly (1 time → 4 times) on each click.

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