docs: 文档清理与重构 — 统一为 3 个核心文档

- 删除 5 个过时/残留文档(project_plan/agent_prompt/optimization_plan/report_db_design/deploy/README)
- 新建 docs/architecture.md(项目架构:11 包职责+数据模型+配置+产物)
- 重写 docs/user-guide.md(CLI 全量+增量/断点续跑+MCP+FAQ)
- 重写 README.md(精简入口+文档索引)
- 更新 continuation.md(追加本次记录)
- 更新 .gitignore(排除 data/* 运行产物)

embedding/factory.py

@@ -0,0 +1,71 @@
+"""Embedding provider 工厂:根据配置构造合适后端。
+
+配置优先级: 显式参数 > configs/llm_models.yaml scenes.embedding > .env > 默认。
+"""
+
+from __future__ import annotations
+
+import os
+
+from configs.loader import load_scene_config
+
+from .base import AsyncEmbeddingProvider, EmbeddingProvider
+from .models import EmbeddingError, EmbeddingProviderType
+from .remote import (
+    DashScopeAsyncEmbeddingProvider,
+    DashScopeEmbeddingProvider,
+)
+
+
+def _read_env(key: str, default: str | None = None) -> str | None:
+    val = os.environ.get(key)
+    if val is None or val.strip() == "":
+        return default
+    return val.strip()
+
+
+def resolve_provider_type(provider: str | None = None) -> EmbeddingProviderType:
+    """根据 provider 参数 / YAML 场景 / env 解析出 EmbeddingProviderType。
+
+    映射:
+        dashscope / qwen / remote     -> DASHSCOPE
+        local / local-bge / bge / bge-m3 -> LOCAL_BGE
+    默认 dashscope。
+    """
+    scene_provider = load_scene_config("embedding").get("provider")
+    p = (
+        provider
+        or scene_provider
+        or _read_env("EMBEDDING_PROVIDER", "dashscope")
+        or "dashscope"
+    ).lower()
+    if p in ("dashscope", "qwen", "remote"):
+        return EmbeddingProviderType.DASHSCOPE
+    if p in ("local", "local-bge", "bge", "bge-m3"):
+        return EmbeddingProviderType.LOCAL_BGE
+    raise EmbeddingError(f"未知 embedding provider: {provider!r}")
+
+
+def make_sync_provider(
+    provider: str | None = None,
+    **kwargs: object,
+) -> EmbeddingProvider:
+    """构造同步 provider。"""
+    pt = resolve_provider_type(provider)
+    if pt == EmbeddingProviderType.DASHSCOPE:
+        return DashScopeEmbeddingProvider(**kwargs)  # type: ignore[arg-type]
+    # 本地后端
+    from .local import LocalBGEEmbeddingProvider
+    return LocalBGEEmbeddingProvider(**kwargs)  # type: ignore[arg-type]
+
+
+def make_async_provider(
+    provider: str | None = None,
+    **kwargs: object,
+) -> AsyncEmbeddingProvider:
+    """构造异步 provider。"""
+    pt = resolve_provider_type(provider)
+    if pt == EmbeddingProviderType.DASHSCOPE:
+        return DashScopeAsyncEmbeddingProvider(**kwargs)  # type: ignore[arg-type]
+    from .local import LocalBGEAsyncEmbeddingProvider
+    return LocalBGEAsyncEmbeddingProvider(**kwargs)  # type: ignore[arg-type]