refactor: 移除多余的override装饰器并整理依赖

1.  移除graph.py和storage.py中多余的typing-extensions override装饰器
2.  精简pyproject.toml的依赖项，移除不必要的typing-extensions
3.  添加mypy作为开发依赖
4.  修复示例代码的类型注解和废弃的赋值使用

src/pyflowx/examples/async_aggregation.py

@@ -10,12 +10,11 @@ Shows:
 from __future__ import annotations
 
 import asyncio
-from typing import Any
 
 import pyflowx as px
 
 
-async def fetch_user(uid: int) -> dict:
+async def fetch_user(uid: int) -> dict[str, object]:
     await asyncio.sleep(0.2)
     return {"id": uid, "name": f"User{uid}"}
 
@@ -26,7 +25,7 @@ async def fetch_posts(uid: int) -> list[int]:
 
 
 # Context annotation → receives the full mapping of upstream results.
-def aggregate(ctx: px.Context) -> dict[str, Any]:
+def aggregate(ctx: px.Context) -> dict[str, object]:
     return dict(ctx)
 
 
@@ -41,7 +40,7 @@ def main() -> None:
     )
 
     print("=== Dry run ===")
-    px.run(graph, strategy="async", dry_run=True)
+    _ = px.run(graph, strategy="async", dry_run=True)
 
     events: list[px.TaskEvent] = []
     print("\n=== Async execution ===")

src/pyflowx/graph.py

@@ -10,8 +10,6 @@ from __future__ import annotations
 import sys
 from typing import Iterable, Mapping, Sequence
 
-from typing_extensions import override
-
 from .errors import CycleError, DuplicateTaskError, MissingDependencyError
 from .task import TaskSpec
 
@@ -240,7 +238,6 @@ class Graph:
             out.append(f"  Layer {layer_idx}: {layer}")
         return "\n".join(out)
 
-    @override
     def __repr__(self) -> str:
         return f"Graph(tasks={len(self._specs)})"
 

src/pyflowx/storage.py

@@ -21,8 +21,6 @@ from abc import ABC, abstractmethod
 from pathlib import Path
 from typing import Any, Mapping
 
-from typing_extensions import override
-
 from .errors import StorageError
 
 
@@ -56,23 +54,18 @@ class MemoryBackend(StateBackend):
     def __init__(self) -> None:
         self._store: dict[str, Any] = {}
 
-    @override
     def load(self) -> Mapping[str, Any]:
         return dict(self._store)
 
-    @override
     def save(self, name: str, value: Any) -> None:
         self._store[name] = value
 
-    @override
     def has(self, name: str) -> bool:
         return name in self._store
 
-    @override
     def get(self, name: str) -> Any:
         return self._store[name]
 
-    @override
     def clear(self) -> None:
         self._store.clear()
 
@@ -110,11 +103,9 @@ class JSONBackend(StateBackend):
         except (OSError, TypeError) as exc:
             raise StorageError(f"cannot write state file {self._path!r}", exc) from exc
 
-    @override
     def load(self) -> Mapping[str, Any]:
         return dict(self._store)
 
-    @override
     def save(self, name: str, value: Any) -> None:
         # 在修改内存状态前先校验可序列化性。
         try:
@@ -126,15 +117,12 @@ class JSONBackend(StateBackend):
         self._store[name] = value
         _ = self._flush()
 
-    @override
     def has(self, name: str) -> bool:
         return name in self._store
 
-    @override
     def get(self, name: str) -> Any:
         return self._store[name]
 
-    @override
     def clear(self) -> None:
         self._store.clear()
         _ = self._flush()