fix(tmux): correct cross-socket sender identity (#808) (#809)

packages/mosaic/framework/tools/tmux/agent-send.sh

@@ -122,12 +122,11 @@ fi
 
 # Source label: this agent's host:session (auto-detected, overridable).
 if [ -z "$SRC_LABEL" ]; then
-  tmux_cmd=(tmux)
-  if [ -n "$SOCKET_NAME" ]; then
-    tmux_cmd+=(-L "$SOCKET_NAME")
-  fi
   src_host=$(hostname -s 2>/dev/null || echo "?")
-  src_sess=$("${tmux_cmd[@]}" display-message -p '#S' 2>/dev/null || echo "?")
+  src_sess=${MOSAIC_AGENT_NAME:-}
+  if [ -z "$src_sess" ]; then
+    src_sess=$(tmux display-message -p '#S' 2>/dev/null || echo "?")
+  fi
   SRC_LABEL="${src_host}:${src_sess}"
 fi