refactor(create): force state isolation by default for new sessions

- Update default ISOLATE value to 1 in create_session.sh
- Add --no-isolate option to allow opting out of directory isolation if desired
- Keep --isolate flag for legacy syntax compatibility

.agents/skills/multi-agent-mux-create/scripts/create_session.sh

@@ -35,8 +35,8 @@ Options:
   --tmux-server NAME  specify isolated tmux server name
   --submit-job PROMPT submit a job to multi-agent-mux-delegate-job registry with the given prompt
   --onboard           automatically submit a project alignment/orientation job to the new agent
-  --isolate           provision an isolated per-session state home (.mam/agent_homes/<uuid>)
-                      so same-CLI multi-role sessions never share a conversation id
+  --no-isolate        disable state isolation (shares global configuration/history)
+                      [default: isolated mode is always active]
   -h, --help          this help
 EOF
 }
@@ -50,7 +50,7 @@ DRY_RUN=0
 TMUX_SERVER_OPT=""
 SUBMIT_JOB_PROMPT=""
 ONBOARD=0
-ISOLATE=0
+ISOLATE=1
 
 while [ $# -gt 0 ]; do
   case "$1" in
@@ -63,7 +63,8 @@ while [ $# -gt 0 ]; do
     --tmux-server) TMUX_SERVER_OPT="$2"; shift 2 ;;
     --submit-job) SUBMIT_JOB_PROMPT="$2"; shift 2 ;;
     --onboard)   ONBOARD=1; shift ;;
-    --isolate)   ISOLATE=1; shift ;;
+    --isolate)   ISOLATE=1; shift ;; # legacy compatibility
+    --no-isolate) ISOLATE=0; shift ;;
     -h|--help)   usage; exit 0 ;;
     *) echo "ERROR: unknown arg: $1" >&2; usage; exit 2 ;;
   esac