Function now_wall_ms 

pub fn now_wall_ms(clock: &dyn Clock) -> u64

The OS wall clock in epoch milliseconds — the same physical source Hlc stamps from. Production reads “now” through an injected clock (Hlc::wall_now_ms); this is for callers that apply a trusted, already- captured changeset against a raw connection with no injected clock (snapshot round-trips, gate/FK mechanics tests), where the honest receiver-now is real wall time and the future-skew bound is incidental, not under test.