chore: add pysnooper dev dependency and update configs

1. add pysnooper>=1.2.3 to dev dependencies in pyproject.toml and uv.lock
2. update type hints in task.py from Iterator to Generator
3. add more PyPI mirrors and update envdev.py comments and checks
4. fix trailing whitespace in executors.py

pyproject.toml

@@ -93,7 +93,10 @@ packages = ["src/pyflowx"]
 pyflowx = { workspace = true }
 
 [dependency-groups]
-dev = ["pyflowx[dev,office,llm]"]
+dev = [
+    "pyflowx[dev,office,llm]",
+    "pysnooper>=1.2.3",
+]
 
 [tool.coverage.run]
 branch      = true