Emits a native event to the live watchers whose pattern matches.
Like the real API, a watcher only hears about a path its pattern selects,
and never an event kind it opted out of through the native ignore flags. A
watcher registered for '**/*.ts' therefore stays silent for a.md — the
fake would otherwise let a test pass while production filtered the event
out.
Patterns currently watched (undisposed), as display strings.
In-memory file-watching capability for tests.