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

docs/gateway/configuration.md

@@ -1803,7 +1803,7 @@ Related docs:
 Notes:
 - `clawdbot gateway` refuses to start unless `gateway.mode` is set to `local` (or you pass the override flag).
 - `gateway.port` controls the single multiplexed port used for WebSocket + HTTP (control UI, hooks, A2UI).
-- Disable the OpenAI-compatible endpoint with `gateway.http.endpoints.chatCompletions.enabled: false`.
+- OpenAI Chat Completions endpoint: **disabled by default**; enable with `gateway.http.endpoints.chatCompletions.enabled: true`.
 - Precedence: `--port` > `CLAWDBOT_GATEWAY_PORT` > `gateway.port` > default `18789`.
 - Non-loopback binds (`lan`/`tailnet`/`auto`) require auth. Use `gateway.auth.token` (or `CLAWDBOT_GATEWAY_TOKEN`).
 - `gateway.remote.token` is **only** for remote CLI calls; it does not enable local gateway auth. `gateway.token` is ignored.

docs/gateway/openai-http-api.md

@@ -5,7 +5,9 @@ read_when:
 ---
 # OpenAI Chat Completions (HTTP)
 
-Clawdbot’s Gateway can serve a small OpenAI-compatible Chat Completions endpoint:
+Clawdbot’s Gateway can serve a small OpenAI-compatible Chat Completions endpoint.
+
+This endpoint is **disabled by default**. Enable it in config first.
 
 - `POST /v1/chat/completions`
 - Same port as the Gateway (WS + HTTP multiplex): `http://<gateway-host>:<port>/v1/chat/completions`
@@ -36,6 +38,22 @@ Or target a specific Clawdbot agent by header:
 Advanced:
 - `x-clawdbot-session-key: <sessionKey>` to fully control session routing.
 
+## Enabling the endpoint
+
+Set `gateway.http.endpoints.chatCompletions.enabled` to `true`:
+
+```json5
+{
+  gateway: {
+    http: {
+      endpoints: {
+        chatCompletions: { enabled: true }
+      }
+    }
+  }
+}
+```
+
 ## Disabling the endpoint
 
 Set `gateway.http.endpoints.chatCompletions.enabled` to `false`: