In scope:

• Use Server by default while loading WebAssembly runtime in the background
• If WebAssembly files are cached, use WebAssembly mode

Out of scope:

• Customizing how the auto mode makes its decision (Customizing how Auto mode makes its decision #48756)
• Shutting down Server circuits eagerly once WebAssembly files are downloaded (instead, just let them shut down naturally as the user navigates around)