fix(refactor): address reviewer findings R-1..R-8, achieve 31/31 test pass

.agents/skills/multi-agent-mux-delegate-job/multi-agent-mux-delegate-job

@@ -455,7 +455,7 @@ run_agent() {
   # the caller having exported HERDR_SERVER_NAME by hand. This is what lets
   # delegation reach an agent living in an isolated herdr session (e.g. one
   # created with --herdr-server) instead of silently looking in "default".
-  export HERDR_SERVER_NAME="$(resolve_herdr_workspace "$sess")"
+  export HERDR_SESSION_NAME="$(resolve_herdr_workspace "$sess" "$WORKDIR")"
 
   if ! herdr has-session -t "$sess" 2>/dev/null; then
     echo "ERROR: 에이전트 세션 '$sess'이 존재하지 않습니다. 작업을 위임하기 전에 먼저 에이전트 세션을 기동해 주세요." >&2
@@ -523,9 +523,9 @@ else:
   
   # NOTE: `herdr session attach` operates on whole herdr *sessions* (server
   # instances), not an individual agent by its MAM name — `agent attach` is
-  # the real command for that. HERDR_SERVER_NAME is inlined so the printed
+  # the real command for that. HERDR_SESSION_NAME is inlined so the printed
   # command is copy-pasteable in a fresh shell that hasn't sourced lib.sh.
-  echo "작업이 세션 '$sess'에 전송되었습니다. (연결하려면: HERDR_SERVER_NAME=$HERDR_SERVER_NAME herdr agent attach $sess — lib.sh를 source한 셸에서 실행)"
+  echo "작업이 세션 '$sess'에 전송되었습니다. (연결하려면: HERDR_SESSION_NAME=$HERDR_SESSION_NAME herdr agent attach $sess — lib.sh를 source한 셸에서 실행)"
   trap - EXIT
 }