## Summary
- Guard `getOrCreateAls` so it no longer calls `new AsyncLocalStorage()`
unconditionally; when the runtime does not expose a usable constructor it
falls back to a no-op store instead of throwing.
- Add a `NoopAsyncLocalStorage` whose `getStore()` returns `undefined`, mirroring
Next.js' `FakeAsyncLocalStorage` and this repo's `async-hooks-stub.ts`.
- Preserve the cross-bundle singleton behavior (`Symbol.for` + `??=`).
## Root Cause
In browser/client bundles `node:async_hooks` can resolve to a stub without a
usable `AsyncLocalStorage` constructor (e.g. Vite's `__vite-browser-external`).
`getOrCreateAls` ran `new AsyncLocalStorage()` at module-eval time, throwing
`TypeError: AsyncLocalStorage is not a constructor`. Because many client-reachable
shims (request-context, headers, cache, …) call this helper on import, the whole
client bundle died and hydration crashed. Checking
`typeof AsyncLocalStorage === "function"` before constructing, with a no-op
fallback, matches Next.js' availability guard.
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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