Add back stubtest check (#1610)

Makefile

@@ -1,6 +1,8 @@
 .DEFAULT_GOAL := all
 sources = python/pydantic_core tests generate_self_schema.py wasm-preview/run_tests.py
 
+mypy-stubtest = uv run python -m mypy.stubtest pydantic_core._pydantic_core --allowlist .mypy-stubtest-allowlist
+
 # using pip install cargo (via maturin via pip) doesn't get the tty handle
 # so doesn't render color without some help
 export CARGO_TERM_COLOR=$(shell (test -t 0 && echo "always") || echo "auto")
@@ -108,6 +110,7 @@ lint-python:
 	uv run ruff check $(sources)
 	uv run ruff format --check $(sources)
 	uv run griffe dump -f -d google -LWARNING -o/dev/null python/pydantic_core
+	$(mypy-stubtest)
 
 .PHONY: lint-rust
 lint-rust: