fix: notify_all on lock timeout to wake blocked readers

When acquire_write or acquire_read times out, call notify_all() before
returning False so waiters blocked by the timed-out thread's presence
(e.g. readers blocked by writer-preference _writers_waiting > 0) are
woken immediately instead of sleeping until the next external notify.

cron/scheduler.py

@@ -504,6 +504,7 @@ class _ReadWriteLock:
                 if deadline is not None:
                     remaining = deadline - time.monotonic()
                     if remaining <= 0:
+                        self._cond.notify_all()
                         return False
                     self._cond.wait(timeout=remaining)
                 else:
@@ -533,6 +534,7 @@ class _ReadWriteLock:
                     if deadline is not None:
                         remaining = deadline - time.monotonic()
                         if remaining <= 0:
+                            self._cond.notify_all()
                             return False
                         self._cond.wait(timeout=remaining)
                     else: