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/main.py

@@ -15,7 +15,6 @@ from fastapi.middleware.cors import CORSMiddleware
 from sqlalchemy.exc import OperationalError
 
 from app.api.router import api_router
-from app.application.agent.confirmation import ConfirmationRegistry
 from app.application.tool_runtime.runtime import ToolRuntime
 from app.core.config import settings
 from app.core.errors import register_exception_handlers, trace_id_var
@@ -71,14 +70,6 @@ async def lifespan(_app: FastAPI) -> AsyncGenerator[None, None]:
         except Exception:  # noqa: BLE001
             log_with_context("SQLite WAL 模式设置失败，已跳过", level="WARNING")
 
-    # 加载模型网关 endpoint 覆盖缓存（DB 优先于 yaml/env）；迁移未完或读失败则降级跳过
-    try:
-        from app.services.ai_provider_admin import reload_provider_manager
-
-        await reload_provider_manager()
-    except Exception:  # noqa: BLE001
-        log_with_context("模型网关覆盖缓存加载失败，已跳过", level="WARNING")
-
     # 运行时注入：事件存储始终就绪（DbEventStore 持久化到 events 表，重启不丢）；
     # 工具运行时依赖沙箱配置，未配置（缺 SANDBOX_AUTH_SECRET 等）则降级 None（工具 API 503）。
     # 事件流与历史查询不依赖沙箱，始终可用。
@@ -122,16 +113,6 @@ async def lifespan(_app: FastAPI) -> AsyncGenerator[None, None]:
 
         _app.state.confirmation_store = DbConfirmationStore(AsyncSessionLocal)
         log_with_context("confirmation_store_set_to_db")
-    # 进程内检查点确认注册表：混合唤醒（同进程 Event + 重启后 DB polling）。
-    _app.state.confirmation_registry = ConfirmationRegistry()
-    from app.application.agent import AgentRunRegistry, discover_python_skills
-
-    _app.state.agent_run_registry = AgentRunRegistry()
-    _app.state.python_skill_catalog = discover_python_skills(("app.skills",))
-    log_with_context(
-        "Python Skills 目录就绪",
-        skills=[skill.name for skill in _app.state.python_skill_catalog.skills],
-    )
     sandbox_http: httpx.AsyncClient | None = None
     tools_http: httpx.AsyncClient | None = None
     if settings.enable_tool_runtime: