fix(#883): warn + bail on unparseable subnet instead of silently writing empty LOCAL_ADDRESS; doc /0 corner case

hive-c0re/src/lifecycle.rs

@@ -101,6 +101,8 @@ pub fn agent_network_ip(name: &str, subnet_cidr: &str) -> Option<String> {
     let prefix_len: u32 = prefix_str.parse().ok()?;
     if prefix_len > 30 {
         // /31 and /32 have no room for agents; /30 has 1 usable slot.
+        // /0 (the other extreme) is handled further down: host_count
+        // overflows checked_shl(32) → 0 → usable = 0 → None.
         return None;
     }
     // Parse dotted-decimal IPv4.