docs: update v1.4.0 changelog

Author: digitallysavvy

changelog.md

@@ -14,13 +14,15 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/).
 - **`AgentSession.think()` / `AsyncAgentSession.think()`** — Send a custom instruction to a running agent through the `agent_management` API.
 - **`Agent.with_interruption()`** — Configure the new top-level `interruption` object for unified interruption control.
 - **MLLM turn detection** — `OpenAIRealtime`, `GeminiLive`, and `VertexAI` now accept `turn_detection`, which maps to `mllm.turn_detection` and overrides top-level turn detection for MLLM sessions.
+- **`audio_scenario` AgentKit support** — `SessionParams` and AgentKit request construction now expose the top-level `parameters.audio_scenario` field.
 - **MLLM vendor parity** — `GeminiLive` is documented and exposed as the direct Google Gemini Live API wrapper.
 
 ### Fixed
 
 - **MiniMax TTS preset stripping** — When a MiniMax reseller preset is inferred (`minimax_speech_2_6_turbo` or `minimax_speech_2_8_turbo`), the `group_id` and `url` fields are now correctly stripped from `tts.params` alongside `key` and `model`. Previously they were forwarded to the API, causing request failures.
 - **MLLM enable flag** — `Agent.with_mllm()` now sets `mllm.enable = True` and removes the deprecated `advanced_features.enable_mllm` flag from generated requests.
 - **MLLM wrapper shape** — MLLM vendors no longer emit removed fields such as `style`; docs and tests now reflect the v2.6 MLLM contract.
+- **Preset-backed OpenAI TTS** — `OpenAITTS` no longer requires `api_key` when a reseller preset supplies credentials server-side.
 - **AgentKit parity coverage** — Added regression coverage for interruption, MLLM turn detection, Deepgram TTS, LLM headers, and deprecated MLLM flag cleanup.
 
 ## [v1.3.0] — 2026-04-02