Add Symbol.asyncDispose to ManagedRuntime

[dmaretskyi]

What is the problem this feature would solve?

Adds compatibility with the JavaScript resource management spec, specifically allowing to use await using syntax with ManagedRuntime

What is the feature you are proposing to solve the problem?

Add Symbol.asyncDispose as an alias to the existing dispose method

What alternatives have you considered?

No response

[codewithkenzo]

Hi! I'd like to work on this enhancement.

My plan:

1. Add Symbol.asyncDispose to the ManagedRuntime interface as an alias to dispose()
2. Implement it in packages/effect/src/internal/managedRuntime.ts
3. Add tests to verify the symbol exists and works correctly

This will enable the await using syntax:

await using runtime = ManagedRuntime.make(MyLayer)
await runtime.runPromise(myEffect)
// Automatically disposed when leaving scope

I'll submit a PR shortly.