Gateway: disable OpenAI HTTP chat completions by default (#686)

* feat(gateway): disable OpenAI chat completions HTTP by default

* test(gateway): deflake mock OpenAI tool-calling

* docs(changelog): note OpenAI HTTP endpoint default-off

src/config/schema.ts

@@ -161,7 +161,7 @@ const FIELD_HELP: Record<string, string> = {
   "gateway.controlUi.basePath":
     "Optional URL prefix where the Control UI is served (e.g. /clawdbot).",
   "gateway.http.endpoints.chatCompletions.enabled":
-    "Enable the OpenAI-compatible `POST /v1/chat/completions` endpoint (default: true).",
+    "Enable the OpenAI-compatible `POST /v1/chat/completions` endpoint (default: false).",
   "gateway.reload.mode":
     'Hot reload strategy for config changes ("hybrid" recommended).',
   "gateway.reload.debounceMs":

src/config/types.ts

@@ -1158,7 +1158,7 @@ export type GatewayReloadConfig = {
 export type GatewayHttpChatCompletionsConfig = {
   /**
    * If false, the Gateway will not serve `POST /v1/chat/completions`.
-   * Default: true when absent.
+   * Default: false when absent.
    */
   enabled?: boolean;
 };