cultmesh-ts: stop the NextEventAsyncFn doc comment from tripping the async-callback grep

The `.async` literal in the doc comment for `NextEventAsyncFn` matched
the "negative grep: no koffi callbacks, .async only on nextEvent" test's
`/\.async\b/g` scan, and the 40 characters before it didn't mention
`nextEvent`, so the test failed on prose, not on a real second async
callsite. Reworded to describe koffi's async export without the
literal `.async` token.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

packages/cultmesh-ts/src/realtime-quic-native.ts

@@ -89,7 +89,7 @@ interface NativeEventStruct {
 type KoffiLib = any;
 
 /** `nextEventAsync`'s signature, typed explicitly because `promisify` cannot
- * infer one from koffi's untyped (`any`) `.async` function. */
+ * infer one from koffi's untyped (`any`) async export. */
 type NextEventAsyncFn = (
   runtime: CultMeshQuicNativeHandle,
   timeoutMs: number,