fix: foreground mode saves node PID and clears OWNER_PID on Windows/MSYS2

Verified on real Windows Git Bash: lifecycle test passed 12/12, manual start/stop released the port, and no brainstorm node processes remained.

skills/brainstorming/scripts/start-server.sh

@@ -107,10 +107,23 @@ if [[ -z "$OWNER_PID" || "$OWNER_PID" == "1" ]]; then
   OWNER_PID="$PPID"
 fi
 
+# Windows/MSYS2: Node.js cannot see POSIX PIDs from the MSYS2 namespace.
+# Passing a PID node cannot verify causes server to log owner-pid-invalid
+# and self-terminate at the 60-second lifecycle check. Clear it so the
+# watchdog is disabled and the idle timeout becomes the only shutdown trigger.
+case "${OSTYPE:-}" in
+  msys*|cygwin*|mingw*) OWNER_PID="" ;;
+esac
+if [[ -n "${MSYSTEM:-}" ]]; then
+  OWNER_PID=""
+fi
+
 # Foreground mode for environments that reap detached/background processes.
 if [[ "$FOREGROUND" == "true" ]]; then
-  echo "$$" > "$PID_FILE"
-  env BRAINSTORM_DIR="$SESSION_DIR" BRAINSTORM_HOST="$BIND_HOST" BRAINSTORM_URL_HOST="$URL_HOST" BRAINSTORM_OWNER_PID="$OWNER_PID" node server.cjs
+  env BRAINSTORM_DIR="$SESSION_DIR" BRAINSTORM_HOST="$BIND_HOST" BRAINSTORM_URL_HOST="$URL_HOST" BRAINSTORM_OWNER_PID="$OWNER_PID" node server.cjs &
+  SERVER_PID=$!
+  echo "$SERVER_PID" > "$PID_FILE"
+  wait "$SERVER_PID"
   exit $?
 fi