fix(amazonq): set Q_WORKER_THREADS only when setting is >0 (aws#4766)

Author: grant0417

.changes/next-release/bugfix-a5c03c3c-3d5c-454b-8d52-1d125ca0a5cc.json

@@ -0,0 +1,4 @@
+{
+  "type" : "bugfix",
+  "description" : "fix(amazonq): Amazon Q chat `@workspace` uses more than 20% cpu"
+}

plugins/amazonq/chat/jetbrains-community/src/software/aws/toolkits/jetbrains/services/cwc/editor/context/project/EncoderServer.kt

@@ -118,10 +118,12 @@ class EncoderServer(val project: Project) : Disposable {
         val map = mutableMapOf<String, String>(
             "PORT" to port.toString(),
             "START_AMAZONQ_LSP" to "true",
-            "Q_WORKER_THREADS" to threadCount.toString(),
             "CACHE_DIR" to cachePath.toString(),
             "MODEL_DIR" to cachePath.resolve("qserver").toString()
         )
+        if (threadCount > 0) {
+            map["Q_WORKER_THREADS"] = threadCount.toString()
+        }
         if (isGpuEnabled) {
             map["Q_ENABLE_GPU"] = "true"
         }