chore: migrate Python type checking to ty (#8002)

## Summary
- replace Python lint type-checking from mypy to ty across LangGraph
packages
- remove mypy config/cache wiring and mypy-only references
- regenerate uv locks with ty 0.0.43

## Verification
- git diff --check
- make lint_package && make lint_tests in libs/langgraph
- make lint_package && make lint_tests in libs/checkpoint
- make lint_package && make lint_tests in libs/checkpoint-sqlite
- make lint_package && make lint_tests in libs/checkpoint-postgres
- make lint_package && make lint_tests in libs/prebuilt
- make lint_package && make lint_tests in libs/cli
- make lint in libs/sdk-py
- make lint in libs/checkpoint-conformance

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: open-swe[bot] <215916821+open-swe[bot]@users.noreply.github.com>

libs/cli/python-monorepo-example/pyproject.toml

@@ -19,7 +19,7 @@ members = ["apps/*", "libs/shared"]
 shared = { workspace = true }
 
 [project.optional-dependencies]
-dev = ["mypy>=1.11.1", "ruff>=0.6.1"]
+dev = ["ruff>=0.6.1", "ty"]
 
 [build-system]
 requires = ["setuptools>=73.0.0", "wheel"]
@@ -43,4 +43,4 @@ lint.ignore = [
 ]
 
 [tool.ruff.lint.pydocstyle]
-convention = "google"
+convention = "google"