feat: 补全 A 股历史资金流向序列功能

1. 新增命令：实现 GetHistoryFundFlowCmd (0x052d Category 22) 用于拉取历史资金分布。
2. 新增模型：增加 HistoricalFundFlow 结构，支持超大/大/中/小单的双向统计。
3. 客户端 API：TdxClient/AsyncTdxClient 增加 get_history_fund_flow() 接口。
4. 单元测试：在 test_a_share_extensions.py 中增加响应包解析逻辑验证。
5. 文档更新：README.md 同步 API 及数据模型定义。

src/xmtdx/client.py

@@ -8,6 +8,7 @@ from .commands.base import BaseCommand
 from .commands.block_info import GetBlockInfoCmd, GetBlockInfoMetaCmd
 from .commands.company_info import GetCompanyInfoCategoryCmd, GetCompanyInfoContentCmd
 from .commands.finance_info import GetFinanceInfoCmd
+from .commands.fund_flow import GetHistoryFundFlowCmd
 from .commands.report_file import GetReportFileCmd
 from .commands.minute_time import GetHistoryMinuteTimeDataCmd, GetMinuteTimeDataCmd
 from .commands.security_bars import GetIndexBarsCmd, GetSecurityBarsCmd
@@ -24,7 +25,7 @@ from .models.enums import KlineCategory, Market
 from .models.finance import CompanyInfoCategory, FinanceInfo, TdxBlock, XdxrRecord
 from .models.quote import SecurityQuote
 from .models.security import SecurityInfo
-from .models.stats import FundFlow, MarketStat
+from .models.stats import FundFlow, HistoricalFundFlow, MarketStat
 from .models.timeseries import MinuteBar, TransactionRecord
 from .transport.async_ import AsyncTdxConnection
 from .transport.sync import KNOWN_HOSTS, TdxConnection, ping_all
@@ -362,6 +363,12 @@ class TdxClient:
                 
         return FundFlow(**stats)
 
+    def get_history_fund_flow(
+        self, market: Market, code: str, start: int, count: int
+    ) -> list[HistoricalFundFlow]:
+        """获取个股历史日线资金流向序列（Category 22）。"""
+        return self._execute(GetHistoryFundFlowCmd(market, code, start, count))
+
 
 # ============================================================
 # 异步客户端
@@ -664,3 +671,9 @@ class AsyncTdxClient:
                 stats[f"small_{direction}"] += amount
         return FundFlow(**stats)
 
+    async def get_history_fund_flow(
+        self, market: Market, code: str, start: int, count: int
+    ) -> list[HistoricalFundFlow]:
+        """获取个股历史日线资金流向序列。"""
+        return await self._execute(GetHistoryFundFlowCmd(market, code, start, count))
+

src/xmtdx/commands/fund_flow.py

@@ -0,0 +1,83 @@
+"""历史资金流向命令 (Category 22)。"""
+
+import struct
+
+from .._binary import slice_bytes, unpack_from
+from ..codec.volume import _decode_volume
+from ..exceptions import TdxDecodeError
+from ..models.enums import Market
+from ..models.stats import HistoricalFundFlow
+from .base import BaseCommand
+
+
+class GetHistoryFundFlowCmd(BaseCommand[list[HistoricalFundFlow]]):
+    """获取历史日线资金流向序列。"""
+
+    def __init__(self, market: Market, code: str, start: int, count: int) -> None:
+        self.market = market
+        self.code = code.encode("utf-8")
+        self.start = start
+        self.count = count
+
+    def build_request(self) -> bytes:
+        # 使用 0x052d 指令（K 线类指令）
+        # 负载长度固定为 28 字节 (0x1c)
+        payload_len = 0x1c
+        header = struct.pack(
+            "<HIHHH",
+            0x010c,
+            0x01016408, # 注意此处标志位与普通行情略有不同
+            payload_len,
+            payload_len,
+            0x052d,
+        )
+        # 参数包：Market(B), Code(6s), Category(H=22), Unknown(H=1), Start(I), Count(I), 3个Unknown(H)
+        params = struct.pack(
+            "<B6sHHIIHHH",
+            int(self.market),
+            self.code,
+            22, # Category 22
+            1,  # Unknown
+            self.start,
+            self.count,
+            0, 0, 0
+        )
+        return header + params
+
+    def parse_response(self, body: bytes) -> list[HistoricalFundFlow]:
+        # 响应格式：9字节头 + 2字节数量 + 每条记录 36 字节
+        if len(body) < 11:
+            return []
+            
+        (num,) = struct.unpack("<H", body[9:11])
+        pos = 11
+        results = []
+        
+        for _ in range(num):
+            if len(body) < pos + 36:
+                break
+            
+            # 记录格式：4字节日期 + 8个4字节自定义浮点金额
+            # [0]日期, [1..4]流入(超/大/中/小), [5..8]流出(超/大/中/小)
+            # 这里的 i 是 uint32 原始字节，随后需用 _decode_volume 解码
+            raw_data = struct.unpack("<Iiiiiiiii", body[pos:pos+36])
+            
+            raw_date = raw_data[0]
+            year = raw_date // 10000
+            month = (raw_date // 100) % 100
+            day = raw_date % 100
+            
+            results.append(HistoricalFundFlow(
+                year=year, month=month, day=day,
+                super_in=_decode_volume(raw_data[1]),
+                large_in=_decode_volume(raw_data[2]),
+                medium_in=_decode_volume(raw_data[3]),
+                small_in=_decode_volume(raw_data[4]),
+                super_out=_decode_volume(raw_data[5]),
+                large_out=_decode_volume(raw_data[6]),
+                medium_out=_decode_volume(raw_data[7]),
+                small_out=_decode_volume(raw_data[8]),
+            ))
+            pos += 36
+            
+        return results

src/xmtdx/models/stats.py

@@ -38,3 +38,27 @@ class FundFlow:
         """全单净流入。"""
         return (self.super_in + self.large_in + self.medium_in + self.small_in) - \
                (self.super_out + self.large_out + self.medium_out + self.small_out)
+
+
+@dataclass
+class HistoricalFundFlow:
+    """历史日线资金流向条目。"""
+    
+    year: int
+    month: int
+    day: int
+    
+    # 金额项 (单位：元)
+    super_in: float
+    super_out: float
+    large_in: float
+    large_out: float
+    medium_in: float
+    medium_out: float
+    small_in: float
+    small_out: float
+    
+    @property
+    def main_net_inflow(self) -> float:
+        """当日主力净流入。"""
+        return (self.super_in + self.large_in) - (self.super_out + self.large_out)