[fit] fix thread leaks from deactivated MCP server channels (#214)

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

* [fit] improve the naming.

Author: loveTsong

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

@@ -88,19 +88,22 @@ public McpServerController(@Fit(alias = "json") ObjectSerializer serializer, Mcp
             if (MapUtils.isEmpty(this.responses)) {
                 return;
             }
-            List<String> toRemoved = new ArrayList<>();
+            List<String> obsoleteSessionIds = new ArrayList<>();
             for (Map.Entry<String, HttpClassicServerResponse> entry : this.responses.entrySet()) {
                 if (entry.getValue().isActive()) {
                     continue;
                 }
-                toRemoved.add(entry.getKey());
+                obsoleteSessionIds.add(entry.getKey());
             }
-            if (CollectionUtils.isEmpty(toRemoved)) {
+            if (CollectionUtils.isEmpty(obsoleteSessionIds)) {
                 return;
             }
-            toRemoved.forEach(this.responses::remove);
-            toRemoved.forEach(this.emitters::remove);
-            log.info("Channels are inactive, remove emitters and responses. [sessionIds={}]", toRemoved);
+            obsoleteSessionIds.forEach(this.responses::remove);
+            for (String obsoleteSessionId : obsoleteSessionIds) {
+                Emitter<TextEvent> removed = this.emitters.remove(obsoleteSessionId);
+                removed.complete();
+            }
+            log.info("Channels are inactive, remove emitters and responses. [sessionIds={}]", obsoleteSessionIds);
         }).build());
     }