Refactor WebSocket authentication handling by removing auth requirements from the hello message. Update related documentation and schemas to reflect the changes in authentication strategy, simplifying the connection process.

engine/docs/ws_v1_schema.md

@@ -33,18 +33,12 @@ If order is violated, server emits `error` with `code = "protocol.order"`.
 ```json
 {
   "type": "hello",
-  "version": "v1",
-  "auth": {
-    "apiKey": "optional-api-key",
-    "jwt": "optional-jwt"
-  }
+  "version": "v1"
 }
 ```
 
 Rules:
 - `version` must be `v1`.
-- If `WS_API_KEY` is configured on server, `auth.apiKey` must match.
-- If `WS_REQUIRE_AUTH=true`, either `auth.apiKey` or `auth.jwt` must be present.
 
 ### `session.start`
 
@@ -205,7 +199,7 @@ Common events:
   - `trackId` convention:
     - `audio_in` for `stage in {audio, asr}`
     - `audio_out` for `stage in {llm, tts, tool}`
-    - `control` otherwise (including protocol/auth errors)
+    - `control` otherwise (including protocol errors)
 
 Track IDs (MVP fixed values):
 - `audio_in`: ASR/VAD input-side events (`input.*`, `transcript.*`)