fix: events and checked prop in Radio

[acstll]

With the current radio button implementation, the scaleChange event is being fired only once. This makes it impossible to hook with framework's state/models.

This PR fixes that.

(It also fixes the click event being fired twice while clicking on the label.)

Why

input[type="radio"] elements only fire change events after user input and only when being actually checked, not unchecked (there is no change event while being unchecked). Since our component relies on this change event to update its checked property, this remains true forever after the first change event. And, since the scaleChange event gets fired using a watcher on this same checked prop, it fires only once: the one time checked changes from false to true.

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Some inspiration: https://github.com/shoelace-style/shoelace/blob/next/src/components/radio/radio.ts