fix(kqueue): preserve create events when child watch fails

[paralin]

This keeps directory Create notifications observable even when registering the new child watch fails, while still registering successful child watches before delivering Create so a following Write is not missed.

Tested with go test ./....

[mattn]

Could you please rebase master?

[paralin]

@mattn rebased!

[mattn]

Thanks for the patch. A few issues need to be addressed before this can land:

1. watcher_darwin.go was switched to an FSEvents-based purego backend in Replace cgo FSEvents backend with purego implementation #9, so the darwin chunk no longer applies. Please rebase and drop the darwin hunk (or move the change into the kqueue paths only). (Resolved by the latest rebase.)
2. Could you clarify the failure mode this targets? openLocked can fail for many reasons (ENOENT race, EACCES, fd exhaustion). Emitting Create without a registered watch means the caller will never see subsequent Write/Remove for that path. Consider also surfacing the registration error via Errors.
3. TestFileCreateWriteRace does not appear to exercise the failure path the fix targets — openLocked will succeed for a normal os.Create. Could you add a test that actually fails on main without this patch (e.g., simulate the registration failure)?
4. Minor: please consolidate added = append(...) into a single line covering both branches, and add a brief comment explaining why we still emit Create on registration failure.

Also, the branch now conflicts with main (likely due to #12); please rebase once more.