feat: Implement agent heartbeat with mTLS and node status tracking

internal/cli/join.go

@@ -36,7 +36,7 @@ type JoinResponse struct {
 }
 
 // JoinCluster sends a join request to the leader and processes the response
-func JoinCluster(leaderAPI, advertiseAddr, nodeName, leaderCACert string, pkiDir string) error {
+func JoinCluster(leaderAPI, advertiseAddr, nodeName, leaderCACert string, pkiDir string) (*JoinResponse, error) {
 	// Create PKI directory if it doesn't exist
 	if err := os.MkdirAll(pkiDir, 0700); err != nil {
 		return fmt.Errorf("failed to create PKI directory: %w", err)
@@ -164,5 +164,5 @@ func JoinCluster(leaderAPI, advertiseAddr, nodeName, leaderCACert string, pkiDir
 		log.Printf("Etcd join instructions: %s", joinResp.EtcdJoinInstructions)
 	}
 
-	return nil
+	return &joinResp, nil
 }