fix(stop): a registry that cannot be read is not "no row" (Issue #71)

load_state_json printed {} on a YAML/DB read error, so a registered
session was closed row-less (exit 0) and its stop workflow skipped.
stop now reads the registry strictly and exits 1 before any herdr call.
Pins of the shifted stop_session.sh lines updated.

Refs #71

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.agents/skills/multi-agent-mux-stop/scripts/stop_session.sh

@@ -166,7 +166,12 @@ sys.exit(0 if cwd == root or cwd.startswith(root + os.sep) else 1)
 
 # 세션이 YAML 에 있는지 + 해당 row 의 워크스페이스 cwd 및 delegate_job_id 추출.
 # JSON 으로 emit — cwd 에 '|' 가 들어가도 안전 (review item 7; 기존 cwd|jid 파서 대체).
-MAPPED_DATA=$(MAM_STATE_JSON="$(load_state_json)" SESSION_NAME="$SESSION_NAME" python3 -c "
+# A registry that cannot be read is not "no row" (Issue #71): stop before herdr.
+STATE_JSON=$(load_state_json strict) || {
+  echo "ERROR: cannot read $AGENT_SESSIONS_YAML, so whether '$SESSION_NAME' has a row is unknown. Nothing changed." >&2
+  exit 1
+}
+MAPPED_DATA=$(MAM_STATE_JSON="$STATE_JSON" SESSION_NAME="$SESSION_NAME" python3 -c "
 import sys, os, json
 name = os.environ['SESSION_NAME']
 d = json.loads(os.environ.get('MAM_STATE_JSON', '{}'))