feat(skills): implement state loader DRY (OP-5) and Job-centric directory structure

- Extract load_state_json centralized helper inside lib.sh to unify state querying
- Refactor status, resume, stop, and monitor scripts to fetch state via MAM_STATE_JSON env var to avoid stdin pipeline collisions
- Restructure delegate-job to provision .mam/jobs/<job_id>/brief.md and direct agents to it, minimizing token size and preventing TUI paste freezes
- Harden send_keys_safe submission loop with was_popup state capture and edge case guards, preventing timing spin false-positives
- Passed cross-verification approved PASS from Planner Claude session

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

@@ -83,44 +83,18 @@ fi
 
 # 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=$(env_python "$AGENT_SESSIONS_YAML" SESSION_NAME="$SESSION_NAME" <<'PYEOF'
-import os, sys, json, yaml, sqlite3
+MAPPED_DATA=$(MAM_STATE_JSON="$(load_state_json)" SESSION_NAME="$SESSION_NAME" python3 -c "
+import sys, os, json
 name = os.environ['SESSION_NAME']
-yaml_path = os.environ['YAML_PATH']
-db_path = os.path.splitext(yaml_path)[0] + '.db'
-d = {}
-try:
-    if os.path.exists(db_path):
-        conn = sqlite3.connect(db_path, timeout=60.0)
-        try:
-            row = conn.execute('SELECT data FROM sessions WHERE name=?', (name,)).fetchone()
-            if row:
-                s = json.loads(row[0])
-                cwd = (s.get('pane') or {}).get('cwd', '')
-                jid = s.get('delegate_job_id', '') or ''
-                print(json.dumps({"cwd": cwd, "job_id": jid}))
-                raise SystemExit(0)
-        except sqlite3.OperationalError:
-            pass
-        row = conn.execute('SELECT data FROM state WHERE id=1').fetchone()
-        if row:
-            d = json.loads(row[0])
-        conn.close()
-    elif os.path.exists(yaml_path):
-        with open(yaml_path) as f:
-            d = yaml.safe_load(f) or {}
-except Exception:
-    pass
-
+d = json.loads(os.environ.get('MAM_STATE_JSON', '{}'))
 for s in d.get('tmux_sessions', []):
     if s.get('name') == name:
         cwd = (s.get('pane') or {}).get('cwd', '')
         jid = s.get('delegate_job_id', '') or ''
-        print(json.dumps({"cwd": cwd, "job_id": jid}))
-        raise SystemExit(0)
-raise SystemExit(7)
-PYEOF
-) || {
+        print(json.dumps({'cwd': cwd, 'job_id': jid}))
+        sys.exit(0)
+sys.exit(7)
+") || {
   echo "ERROR: session '$SESSION_NAME' not in $AGENT_SESSIONS_YAML" >&2
   exit 1
 }