[fel] ensure thread release during channel cleanup by triggering completion

Author: loveTsong

framework/fel/java/plugins/tool-mcp-server/src/main/java/modelengine/fel/tool/mcp/server/McpServerController.java

@@ -99,7 +99,10 @@ public McpServerController(@Fit(alias = "json") ObjectSerializer serializer, Mcp
                 return;
             }
             toRemoved.forEach(this.responses::remove);
-            toRemoved.forEach(this.emitters::remove);
+            for (String s : toRemoved) {
+                Emitter<TextEvent> removed = this.emitters.remove(s);
+                removed.complete();
+            }
             log.info("Channels are inactive, remove emitters and responses. [sessionIds={}]", toRemoved);
         }).build());
     }