fix: preserve *args/**kwargs docstring descriptions in tool schemas

[TheSaiEaranti]

Summary

Google and NumPy style docstrings write variadic parameters with their stars (*numbers:, **kwargs:), and griffe returns those names verbatim. generate_func_documentation keyed param_descriptions by that verbatim name, while function_schema looks descriptions up by the bare signature parameter name — so *args/**kwargs descriptions were silently dropped from the tool JSON schema for those two styles. Sphinx style (:param numbers:) has no stars and carried them through, and function_schema already plumbs the description into the VAR_POSITIONAL/VAR_KEYWORD Field(...) calls, so the loss was purely a key mismatch. griffe warnings are suppressed during parsing, which made it fully silent.

The fix strips the stars when building the description map (param.name.lstrip("*")). Python identifiers cannot begin with *, so this is a no-op for every non-variadic key.

Before, documenting the same function per each style's own convention behaved inconsistently:

google_style:   'numbers': None            'kwargs': None
numpy_style:    'numbers': None            'kwargs': None
sphinx_style:   'numbers': 'the numbers …' 'kwargs': 'extra options.'

After, all three styles carry the descriptions into params_json_schema.

Test plan

• Added test_variadic_param_descriptions_preserved, parametrized over google/numpy/sphinx docstrings for the same (x, *numbers, **kwargs) function, asserting all three descriptions land in the schema properties. The google and numpy cases fail without the fix; sphinx passes before and after, pinning the consistency claim.
• make format, make lint, make typecheck (mypy + pyright), and make tests all pass locally.

Issue number

None — found while reading function_schema.py.

Checks

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