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)

dedup/__init__.py

@@ -0,0 +1,44 @@
+"""三层新闻去重模块 (M3)。
+
+公共 API:
+    - Deduper:         主类(check / ingest / stats)
+    - FingerprintStore: SQLite 指纹库(底层,通常无需直接用)
+    - DedupResult / DedupLayer / DedupStats / Fingerprint: 数据模型
+    - simhash64 / hamming / content_hash / normalize_content: 指纹算法
+"""
+
+from .deduper import (
+    DEFAULT_TIME_WINDOW_DAYS,
+    Deduper,
+    article_to_fingerprint,
+)
+from .hasher import (
+    DEFAULT_HAMMING_THRESHOLD,
+    NGRAM_SIZE,
+    SIMHASH_BITS,
+    content_hash,
+    hamming,
+    normalize_content,
+    simhash64,
+)
+from .models import DedupLayer, DedupResult, DedupStats, Fingerprint
+from .store import DEFAULT_DB_PATH, FingerprintStore
+
+__all__ = [
+    "DEFAULT_DB_PATH",
+    "DEFAULT_HAMMING_THRESHOLD",
+    "DEFAULT_TIME_WINDOW_DAYS",
+    "NGRAM_SIZE",
+    "SIMHASH_BITS",
+    "DedupLayer",
+    "DedupResult",
+    "DedupStats",
+    "Deduper",
+    "Fingerprint",
+    "FingerprintStore",
+    "article_to_fingerprint",
+    "content_hash",
+    "hamming",
+    "normalize_content",
+    "simhash64",
+]