rebuild re-registers agent; preserve /run/hyperhive across restarts

hive-c0re/src/coordinator.rs

@@ -26,6 +26,9 @@ impl Coordinator {
     }
 
     pub async fn register_agent(&self, name: &str) -> Result<PathBuf> {
+        // Idempotent: drop any existing listener so re-registration (e.g. on rebuild,
+        // or after a hive-c0re restart cleared /run/hyperhive) gets a fresh socket.
+        self.unregister_agent(name);
         let agent_dir = Self::agent_dir(name);
         std::fs::create_dir_all(&agent_dir)
             .with_context(|| format!("create agent dir {}", agent_dir.display()))?;