feat(client): add durable HTTP task state

client/src/cmbuyer_client/runtime.py

@@ -5,6 +5,7 @@ from __future__ import annotations
 from dataclasses import dataclass
 import os
 from pathlib import Path
+from typing import Any, Callable
 
 
 @dataclass(frozen=True)
@@ -17,21 +18,34 @@ class RuntimePaths:
     root: Path
     logs: Path
     artifacts: Path
+    state: Path
+    database: Path
 
     @classmethod
     def from_root(cls, root: Path) -> "RuntimePaths":
-        resolved_root = root.expanduser()
+        # 路径在进程启动时一次性固化；之后 cwd 改变不能打开第二套数据库或绕过原 mutex。
+        resolved_root = root.expanduser().resolve(strict=False)
+        state = resolved_root / "state"
         return cls(
             root=resolved_root,
             logs=resolved_root / "logs",
             artifacts=resolved_root / "artifacts",
+            state=state,
+            database=state / "client-state.sqlite3",
         )
 
     @classmethod
     def default(cls) -> "RuntimePaths":
         local_app_data = os.environ.get("LOCALAPPDATA")
         if local_app_data:
-            return cls.from_root(Path(local_app_data) / "cmbuyer")
+            local_root = Path(local_app_data).expanduser()
+            if not local_root.is_absolute():
+                raise RuntimeError("local_app_data_must_be_absolute")
+            return cls.from_root(local_root / "cmbuyer")
+
+        if os.name == "nt":
+            # Windows 上回退到 home 会悄悄创建第二套状态库并绕开同一 mutex，必须失败闭合。
+            raise RuntimeError("local_app_data_required")
 
         return cls.from_root(Path.home() / ".local" / "share" / "cmbuyer")
 
@@ -40,3 +54,49 @@ class RuntimePaths:
 
         self.logs.mkdir(parents=True, exist_ok=True)
         self.artifacts.mkdir(parents=True, exist_ok=True)
+        self.state.mkdir(parents=True, exist_ok=True)
+
+
+@dataclass
+class LocalStateRuntime:
+    """持有 named mutex 与本地状态库，保证 mutex 总是先取得。"""
+
+    paths: RuntimePaths
+    mutex: Any
+    store: Any
+
+    @classmethod
+    def open(
+        cls,
+        paths: RuntimePaths | None = None,
+        *,
+        mutex_factory: Callable[[Path], Any] | None = None,
+        protector_factory: Callable[[], Any] | None = None,
+        store_factory: Callable[[Path, Any], Any] | None = None,
+    ) -> "LocalStateRuntime":
+        from .localstate.protection import DpapiProtector
+        from .localstate.single_instance import NamedMutex
+        from .localstate.store import LocalStateStore
+
+        selected = paths or RuntimePaths.default()
+        selected.ensure_exists()
+        make_mutex = mutex_factory or NamedMutex
+        make_protector = protector_factory or DpapiProtector
+        make_store = store_factory or LocalStateStore
+        mutex = make_mutex(selected.database)
+        try:
+            protector = make_protector()
+            store = make_store(selected.database, protector)
+        except Exception:
+            mutex.close()
+            raise
+        return cls(selected, mutex, store)
+
+    def close(self) -> None:
+        self.mutex.close()
+
+    def __enter__(self) -> "LocalStateRuntime":
+        return self
+
+    def __exit__(self, exc_type: object, exc: object, traceback: object) -> None:
+        self.close()