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/loose_ends.rs

@@ -13,12 +13,12 @@
 //! the dashboard uses, so the bottleneck would be json
 //! (de)serialisation, not the read.
 
-use std::time::{SystemTime, UNIX_EPOCH};
 
 use anyhow::Result;
 use hive_sh4re::LooseEnd;
 
 use crate::coordinator::Coordinator;
+use hive_sh4re::wire_time::now_unix;
 
 /// Open threads pending against `agent`:
 /// - undelivered inbox messages this agent still owes itself a `recv`
@@ -143,13 +143,6 @@ fn saturating_age(now: i64, then: i64) -> u64 {
     u64::try_from(delta).unwrap_or(0)
 }
 
-fn now_unix() -> i64 {
-    SystemTime::now()
-        .duration_since(UNIX_EPOCH)
-        .ok()
-        .and_then(|d| i64::try_from(d.as_secs()).ok())
-        .unwrap_or(0)
-}
 
 #[cfg(test)]
 mod tests {