feat: add extended market, offline data reader, rewrite README

- Add ExTdxClient/AsyncExTdxClient for futures, HK stocks, etc (port 7727)
- Add offline module: read daily bars, minute bars, blocks, gbbq, financials
  from local TDX installation directory (inspired by pytdx)
- Add examples 09 (file download) and 10 (offline data reading)
- Rewrite README with comprehensive API docs and code examples
- Add TdxFileNotFoundError and TdxOfflineError exceptions

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

examples/10_offline/block_data.py

@@ -0,0 +1,80 @@
+"""演示：板块数据读取（本地 + 网络自动回退）。
+
+系统板块获取优先级：
+  1. 本地 .dat 文件（离线读取）
+  2. TDX 服务器在线获取（自动回退）
+
+自定义板块仅支持本地读取。
+"""
+
+from pathlib import Path
+
+from xmtdx import TdxClient
+from xmtdx.models.finance import TdxBlock
+from xmtdx.offline import detect_tdx_home, read_block_dat, read_customer_blocks
+
+
+def _print_blocks(blocks: list[TdxBlock], title: str) -> None:
+    print(f"\n{title} ({len(blocks)} 个板块):")
+    for block in blocks[:5]:
+        codes_preview = ", ".join(block.codes[:5])
+        suffix = "..." if len(block.codes) > 5 else ""
+        print(f"  {block.name} ({block.count}只): {codes_preview}{suffix}")
+    if len(blocks) > 5:
+        print(f"  ... 还有 {len(blocks) - 5} 个板块")
+
+
+home = detect_tdx_home()
+
+# --- 系统板块 ---
+print("=" * 60)
+print("系统板块")
+print("=" * 60)
+
+vipdoc = Path(home) / "vipdoc" if home else None
+block_names = ["block_zs.dat", "block_gn.dat", "block_fg.dat"]
+block_labels = {
+    "block_zs.dat": "行业板块",
+    "block_gn.dat": "概念板块",
+    "block_fg.dat": "风格板块",
+}
+
+need_fetch = []
+for name in block_names:
+    local_path = vipdoc / name if vipdoc else None
+    if local_path and local_path.is_file():
+        blocks = read_block_dat(local_path)
+        _print_blocks(blocks, f"{block_labels[name]} ({name}, 本地)")
+    else:
+        print(f"\n{block_labels[name]}: 本地文件不存在，将从服务器获取")
+        need_fetch.append(name)
+
+# 本地没有的板块，通过网络获取
+if need_fetch:
+    print(f"\n正在连接服务器获取 {len(need_fetch)} 个板块文件...")
+    with TdxClient.from_best_host() as c:
+        for name in need_fetch:
+            blocks = c.get_block_info(name)
+            _print_blocks(blocks, f"{block_labels[name]} ({name}, 网络)")
+
+# --- 自定义板块 ---
+print(f"\n{'=' * 60}")
+print("自定义板块")
+print("=" * 60)
+
+if home:
+    blocknew_dir = Path(home) / "T0002" / "blocknew"
+    if blocknew_dir.is_dir():
+        blocks = read_customer_blocks(blocknew_dir)
+        if blocks:
+            print(f"\n共 {len(blocks)} 个自定义板块:")
+            for block in blocks[:10]:
+                codes_preview = ", ".join(block.codes[:5])
+                suffix = "..." if len(block.codes) > 5 else ""
+                print(f"  {block.blockname} ({len(block.codes)}只): {codes_preview}{suffix}")
+        else:
+            print("未找到自定义板块数据")
+    else:
+        print(f"自定义板块目录不存在: {blocknew_dir}")
+else:
+    print("需要本地通达信安装目录才能读取自定义板块")