fix: prevent responseListeners memory leak in CoreMessenger (continuedev#11901)

Response listeners were only removed when data contained `"done": true`,
but most message types (file events, autocomplete, nextEdit, etc.)
return responses without a `done` field. This caused every fire-and-forget
request to leak its callback lambda permanently in the map.

Over a long session with heavy autocomplete and file navigation, this
could accumulate hundreds of thousands of entries (40-100+ MB).

Fix: invert the removal logic — remove the listener by default, and
only keep it when `done == false` (i.e., a streaming response is still
in progress). This preserves existing streaming behavior while ensuring
all non-streaming responses are cleaned up immediately.

Author: RomneyDa

extensions/intellij/src/main/kotlin/com/github/continuedev/continueintellijextension/continue/CoreMessenger.kt

@@ -65,9 +65,10 @@ class CoreMessenger(
         responseListeners[messageId]?.let { listener ->
             listener(data)
             @Suppress("UNCHECKED_CAST")
-            val done = (data as? Map<String, Boolean>)?.get("done")
+            val done = (data as? Map<String, Any>)?.get("done") as? Boolean
 
-            if (done == true) {
+            // Remove unless explicitly streaming (done == false)
+            if (done != false) {
                 responseListeners.remove(messageId)
             }
         }