feat(video): DashScope video specialist with correct i2v request bodies

- Add video_generation_client: async video-synthesis, t2v vs i2v (Wan 2.7 input.media first_frame vs legacy img_url).

- Coerce *-t2v* to *-i2v* when first frame present; AIA_VIDEO_I2V_INPUT_STYLE / I2V_MODEL overrides.

- Gateway/direct_loop early return for video specialist; workspace video + factory allowlist.

- Normalize WS and admin chat attachments (image_ref parity); mp4 attachment store roundtrip tests.

Co-authored-by: Cursor <cursoragent@cursor.com>

runtime/workspaces/experts.py

@@ -252,7 +252,7 @@ def build_expert_catalog_block(*, include_main: bool = False, per_field_limit: i
 
 def discover_specialist_ids_from_workspaces(
     *,
-    base_order: tuple[str, ...] = ("generalist", "ops", "memory", "image"),
+    base_order: tuple[str, ...] = ("generalist", "ops", "memory", "image", "video"),
 ) -> tuple[str, ...]:
     cache_key = (expert_workspace_signature_token(), tuple(str(x).strip().lower() for x in base_order if str(x).strip()))
     with _CACHE_LOCK:
@@ -291,7 +291,7 @@ def warm_expert_workspace_cache() -> None:
 
 def specialist_registry_snapshot(
     *,
-    base_order: tuple[str, ...] = ("generalist", "ops", "memory", "image"),
+    base_order: tuple[str, ...] = ("generalist", "ops", "memory", "image", "video"),
 ) -> tuple[dict[str, Any], ...]:
     """Single source of truth for runtime specialist discovery and metadata."""
     ordered = discover_specialist_ids_from_workspaces(base_order=base_order)

runtime/workspaces/video/META.json

@@ -0,0 +1,5 @@
+{
+  "display_name_en": "Video generation",
+  "display_name_zh": "视频生成专家",
+  "role": "expert"
+}

runtime/workspaces/video/ROLE_SYSTEM.md

@@ -0,0 +1 @@
+你是视频生成专家：将用户自然语言 prompt 交给 Wan / 百炼 text-to-video API，返回可下载或可播放的成片附件。不要编造已生成视频的 URL；仅展示接口真实返回结果或明确错误。

runtime/workspaces/video/SOUL.md

@@ -0,0 +1,9 @@
+你是**文生视频 / 图生视频**方向的专家助手：根据用户给出的画面与镜头描述（及可选的**首帧参考图**），调用百炼 / DashScope **异步视频合成**接口生成短视频结果，并将产出以会话附件（`video_ref`）形式返回。用户上传图片时，首帧会作为 `img_url` 提交（需使用支持图生视频的 i2v 模型）。
+
+回答要求：
+- 若用户描述含糊，可基于常识补全合理的镜头语言，但避免与用户明确约束相矛盾。
+- 生成失败时给出可读的上游错误或参数提示（如模型与区域、时长、分辨率不匹配）。
+
+边界：
+- 本专家链路**不调用**通用工具循环；仅走专用 HTTP 视频合成与轮询。
+- 不承诺具体成片内容符合版权素材或真人肖像等合规要求；用户需自行确保 prompt 合规。