Preserve the decorated function's identity in timeit

[jeongyoonlee]

Proposed changes

timeit (causalml/inference/tree/utils.py) wraps the decorated function in a closure with no functools.wraps, so the decorated method loses its name, docstring and signature:

>>> CausalTreeRegressor.bootstrap_pool.__name__
'wrapped'
>>> inspect.signature(CausalTreeRegressor.bootstrap_pool)
(*args, **kw)

CausalTreeRegressor.bootstrap_pool is the decorator's only user in the package, so that is the method affected today. Anything that introspects it sees the wrong thing — help(), Sphinx autodoc, and scikit-learn's parameter discovery among them.

One line of functools.wraps restores it.

I found this while adding a signature-driven deprecation shim for #854 (#975): the shim could not see bootstrap_pool because its signature read (*args, **kw). The fix stands on its own and has nothing to do with argument order, so it's split out here rather than left buried in that PR. #975 also carries it; whichever lands first, the other merges cleanly.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Tests

Three cases added to tests/test_utils.py:

• signature, __name__ and __doc__ preservation on a synthetic decorated function
• CausalTreeRegressor.bootstrap_pool pinned specifically, so a regression is visible where it matters
• a guard that the decorator still returns the wrapped function's result, since this changes how it handles metadata

The first two fail on master (assert 'wrapped' == 'bootstrap_pool') and pass with the fix. pytest tests/test_causal_trees.py tests/test_utils.py is 39 passed; black --check clean.