M4b：ai_provider 删除手术①-⑥——神识全面接管模型出口

- ① 后端删除 app/ai_provider/（38 文件，含 anthropic/openai 格式、billing、audio、embedding）、services/ai_provider_admin.py、core/config/model_config.py、tests/ai_provider/（21 文件）
- ② 连带退役 application/agent/（旧 Agent 循环/steer/follow-up/确认注册表）、application/skill_executor.py、app/skills/（python skills 孤儿）、endpoints/audio.py、application/imports.py（ProviderManager 消费方）；settings 端点收敛为生成偏好
- ③ runs.py 修剪：AgentRunRegistry/steer/follow-up/confirmations 端点退役，保留 list/get/events/cancel/stream；safety 确认改为直接落库裁决（pending→approved/denied）
- ④ 前端删除：models 页、ModelGatewayView、gateway.ts、GatewayPanel（玄关）、ModelGatewayPanel/ModelStrategyForm、audio.ts/useVoiceInput、网关类型与 mock；设置页收敛为外观/语言/通知
- ⑤ 配置收敛：config/models|providers|pricing.example.yaml 归档 shenshi/config/；.env.example 删 provider keys/MODEL_ENDPOINT_POOL/MODEL_CONFIG_PATH，收敛 SHENSHI_*
- ⑥ 验收：rg 审计灵台 Provider SDK import 与 ai_provider 引用归零；后端 528 passed（2 个预存失败经 HEAD 复跑验证与本手术无关）、前端 type-check+201 passed、神识 go vet+test、BFF 4 passed

backend/app/schemas/runtime.py

@@ -1,6 +1,6 @@
 """运行时 API schema。"""
 
-from typing import Any, Literal
+from typing import Any
 
 from pydantic import BaseModel, ConfigDict, Field
 
@@ -85,31 +85,3 @@ class RunResponse(BaseModel):
     error_message: str | None = Field(description="失败错误信息；成功时为空。")
     created_at: str = Field(description="创建时间，UTC ISO 8601 字符串。")
     updated_at: str = Field(description="更新时间，UTC ISO 8601 字符串。")
-
-
-class AgentControlRequest(BaseModel):
-    """运行中 steer / follow-up 消息。"""
-
-    content: str = Field(min_length=1, max_length=20_000)
-
-
-class AgentControlResponse(BaseModel):
-    accepted: bool = True
-
-
-class ConfirmationResolutionResponse(BaseModel):
-    """工具确认 resolve 结果（approve/deny 端点成功响应）。"""
-
-    model_config = ConfigDict(
-        json_schema_extra={
-            "examples": [
-                {"status": "resolved", "approved": True},
-                {"status": "resolved", "approved": False},
-            ]
-        }
-    )
-
-    status: Literal["resolved"] = Field(
-        default="resolved", description="恒为 resolved；失败路径由错误响应覆盖。"
-    )
-    approved: bool = Field(description="裁决结果：True=批准，False=拒绝。")