2.0.0-rc Signal update lost when a suspending reader is unmounted #3372

Describe the bug

setShow(true) waits for an async memo. Unmounting its reader before it resolves leaves show() stuck at false, even after all async work finishes.

Your Example Website or App

https://s.olid.uk/id/-oM9acvMQFu_ehAAj-lP4Q

Steps to Reproduce the Bug or Issue

1. Wait two seconds for the initial value to settle.
2. Click Run.
3. Wait for everything to finish. Show stays false.

Expected behavior

Show eventually becomes true. Removing the reader shouldn't lose the update.

Screenshots or Videos

No response

Platform

• OS: Windows
• Browser: Firefox

Additional context

Reproduces on next at 961cc77 and #3337 at 20f3143.

Removing setMounted(false), or increasing the second delay to 1500ms, lets show become true.