refactor: single now_unix in hive_sh4re::wire_time

replaces 15 per-module copies (now_unix/now_secs) across hive-c0re and
hive-ag3nt; wire_time already owns the epoch-seconds convention

hive-c0re/src/scheduled_prompts_worker.rs

@@ -10,6 +10,7 @@ use hive_sh4re::Message;
 
 use crate::coordinator::Coordinator;
 use crate::scheduled_prompts::Schedule;
+use hive_sh4re::wire_time::now_unix;
 
 /// Per-tick cap. Each schedule fires once per tick at most;
 /// 100/tick × 5s tick = sustained throughput cap of ~20/sec,
@@ -236,13 +237,6 @@ fn notify_operator_missing_target(coord: &Coordinator, schedule: &Schedule, targ
     }
 }
 
-fn now_unix() -> i64 {
-    std::time::SystemTime::now()
-        .duration_since(std::time::UNIX_EPOCH)
-        .ok()
-        .and_then(|d| i64::try_from(d.as_secs()).ok())
-        .unwrap_or(0)
-}
 
 /// Per-target outcome counts for one `fire_now` invocation.
 /// Returned to the operator so the dashboard can render