Master depends on `typing_extensions` but doesn't state it

[tare]

Bug Description

Master depends on typing_extensions but does not install it. I think the dependency was introduced in #2028.

CI didn't catch this because the test extra has mypy.

Steps to Reproduce

$ uv venv --python 3.9 
$ source .venv/bin/activate
$ uv pip install numpyro@https://github.com/pyro-ppl/numpyro.git
$ python -c 'import numpyro'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/Users/tarmo.aijo/numpyro_issue_type_extensions/.venv/lib/python3.9/site-packages/numpyro/__init__.py", line 13, in <module>
    from numpyro import compat, diagnostics, distributions, handlers, infer, ops, optim
  File "/Users/tarmo.aijo/numpyro_issue_type_extensions/.venv/lib/python3.9/site-packages/numpyro/distributions/__init__.py", line 4, in <module>
    from numpyro.distributions.conjugate import (
  File "/Users/tarmo.aijo/numpyro_issue_type_extensions/.venv/lib/python3.9/site-packages/numpyro/distributions/conjugate.py", line 13, in <module>
    from numpyro._typing import ConstraintT
  File "/Users/tarmo.aijo/numpyro_issue_type_extensions/.venv/lib/python3.9/site-packages/numpyro/_typing.py", line 9, in <module>
    from typing_extensions import ParamSpec, TypeAlias
ModuleNotFoundError: No module named 'typing_extensions'

Expected Behavior

We shouldn't get ModuleNotFoundError when we import numpyro

$ uv venv --python 3.9 
$ source .venv/bin/activate
$ uv pip install numpyro@https://github.com/pyro-ppl/numpyro.git typing_extensions
$ python -c 'import numpyro'