Feature request: configurable spinner phrase rotation speed

Summary

I'd love a setting to control how quickly spinner verb phrases rotate. The spinnerVerbs setting already lets us customize which phrases appear, but the rotation speed is fixed internally.

Use case

I have a short custom verb list, and at the current rotation speed I end up re-reading the same phrase for a while before it changes. Being able to speed up the cycle would make the experience feel more dynamic — especially for short lists where you'd otherwise stare at the same phrase for several seconds.

This is a different angle from #23418 (which was closed as not planned): the core ask there was a general configurability knob. My argument is more specifically about short verb lists feeling stale at the default interval. When you only have 3–5 custom verbs, the fixed timing that works fine for the default longer list doesn't feel right.

Proposal

A spinnerVerbInterval setting in settings.json, value in milliseconds:

{
  "spinnerVerbInterval": 1500
}

• Default to the current interval so nothing changes for existing users.
• A reasonable minimum (e.g. 200ms) to prevent flickering.

This fits naturally alongside the existing spinnerVerbs, spinnerTipsEnabled, and prefersReducedMotion settings.

Alternatives considered

• Nesting it inside the spinnerVerbs object — works but changes the existing schema shape unnecessarily.
• Auto-scaling interval based on list length — clever but opaque; an explicit setting is simpler and more predictable.