feat!: use alien-signals for reactivity

[littensy]

Rewrite Charm using the alien-signals reactive algorithm.

Why?

Adopting alien-signals brings benefits and guarantees like predictable effect ordering, nested effect cleanup, and more efficient computed() memoization, all without a significant compromise to performance. Building Charm on this signal algorithm should improve Charm's overall efficiency and reliability.

What's New?

• Added effectScope(fn) to clean up a group of effects and subscriptions
• Added onCleanup(fn) to run fn once the current effect/scope reruns or gets disposed
• Added listen(selector, listener) for immediate subscriptions
• Optimized mapped() to cache values and prevent unnecessary updates
• Optimized computed() to use lazy evaluation instead of eager updates

Breaking Changes

• Nested effects automatically dispose when the parent effect reruns or the scope is disposed
  • This applies to subscribe, listen, and observe.
  • Create a "detached" effect scope if you need to run code outside the parent effect's lifecycle.
• Effects created inside the observer function now automatically dispose when the item is removed
• Renamed batch() to batched()
• Renamed peek() to untracked()

Notes

• Effects created in peek() still clean up with the parent effect/scope. Use a detached effectScope to run code that's detached from the parent effect.
• In Roblox Studio, the following flags will be enabled by default:
  • strict: Formerly _G.__DEV__, this bans unsafe yielding and enables additional checks in Charm Sync.
  • frozen: Deep-freeze all atom values to enforce immutable state updates.