Add warning display when player loading is paused due to user interaction

[peppy]

As touched on in #37082.

15 minute task fixing a UX which was definitely not as visible as it should have been.

osu.2026-03-25.at.07.28.49.mp4

[bdach]

Weird behaviours that might be blockers:

The warning display always shows briefly just before loading into the game if you tab out of the game

Screen.Recording.2026-03-25.at.09.34.31.mov

Likely happens because the IsHovered checks all fail due to being tabbed out, until idleTracker kicks in after 1.5s to kick the player into ReadyForGameplay state

The warning display shows briefly on every multiplayer game start

Screen.Recording.2026-03-25.at.09.34.59.mov

Probably corresponds to the RTT between the client notifying the server it's loaded player, and the server acknowledging receipt of that notification.

[peppy]

I almost think loading should be blocked as long as the game doesn't have focus.

For the multiplayer case, I guess we can delay the animation a bit to avoid in most cases?

[bdach]

I almost think loading should be blocked as long as the game doesn't have focus.

I tend to agree but fixing this is probably out of scope here. I'm just mentioning things you might not be okay with before someone else does in five separate issues tomorrow 🤷

[bdach]

maybe fine 🤷