chore: 完成项目汉化与测试覆盖增强

- 将项目文档、注释全量翻译为简体中文
- 新增 coverage 配置并要求 100% 分支覆盖率
- 补充所有模块的单元测试用例，覆盖全分支场景
- 重构执行器代码，提取公共重试与失败逻辑

tests/test_errors.py

@@ -0,0 +1,90 @@
+"""错误类型测试。"""
+
+from __future__ import annotations
+
+import pytest
+
+import pyflowx as px
+from pyflowx.errors import (
+    CycleError,
+    DuplicateTaskError,
+    InjectionError,
+    MissingDependencyError,
+    PyFlowXError,
+    StorageError,
+    TaskFailedError,
+    TaskTimeoutError,
+)
+
+
+def test_all_errors_are_pyflowx_subclass() -> None:
+    assert issubclass(DuplicateTaskError, PyFlowXError)
+    assert issubclass(MissingDependencyError, PyFlowXError)
+    assert issubclass(CycleError, PyFlowXError)
+    assert issubclass(TaskFailedError, PyFlowXError)
+    assert issubclass(TaskTimeoutError, PyFlowXError)
+    assert issubclass(InjectionError, PyFlowXError)
+    assert issubclass(StorageError, PyFlowXError)
+
+
+def test_duplicate_task_error_attributes() -> None:
+    err = DuplicateTaskError("foo")
+    assert err.name == "foo"
+    assert "foo" in str(err)
+
+
+def test_missing_dependency_error_attributes() -> None:
+    err = MissingDependencyError("child", "parent")
+    assert err.task == "child"
+    assert err.dependency == "parent"
+    assert "child" in str(err)
+    assert "parent" in str(err)
+
+
+def test_cycle_error_attributes() -> None:
+    err = CycleError(["a", "b", "c"])
+    assert err.cycle == ["a", "b", "c"]
+    # 链应首尾相接展示
+    assert "a -> b -> c -> a" in str(err)
+
+
+def test_task_failed_error_attributes() -> None:
+    cause = ValueError("boom")
+    err = TaskFailedError(task="t", cause=cause, attempts=3, layer=2)
+    assert err.task == "t"
+    assert err.cause is cause
+    assert err.attempts == 3
+    assert err.layer == 2
+    assert "layer 2" in str(err)
+
+
+def test_task_failed_error_without_layer() -> None:
+    err = TaskFailedError(task="t", cause=RuntimeError("x"), attempts=1)
+    assert err.layer is None
+    assert "layer" not in str(err)
+
+
+def test_task_timeout_error_attributes() -> None:
+    err = TaskTimeoutError(task="t", timeout=1.5)
+    assert err.task == "t"
+    assert err.timeout == 1.5
+    assert "1.500s" in str(err)
+
+
+def test_injection_error_attributes() -> None:
+    err = InjectionError(task="t", detail="missing param")
+    assert err.task == "t"
+    assert "missing param" in str(err)
+
+
+def test_storage_error_with_cause() -> None:
+    cause = OSError("disk full")
+    err = StorageError(detail="write failed", cause=cause)
+    assert err.cause is cause
+    assert "write failed" in str(err)
+
+
+def test_storage_error_without_cause() -> None:
+    err = StorageError(detail="bad")
+    assert err.cause is None
+    assert "bad" in str(err)