Fix args_to_skip validation failure for dict type parameters

[rasdani]

Description

• Filters function signature before schema generation to avoid strict JSON schema validation errors on skipped parameters
• Parameters with dict type (which produce additionalProperties: true) no longer cause validation failures when listed in args_to_skip

Type of Change

• Bug fix (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
• Test improvement

Testing

• All existing tests pass when running uv run pytest locally.
• New tests have been added to cover the changes

Checklist

• My code follows the style guidelines of this project as outlined in AGENTS.md
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published

Additional Notes

---

Note

Improves tool schema generation to prevent JSON schema validation errors when skipping arguments.

• Adds filter_signature to wrap functions with a filtered signature/annotations (non-destructive) for schema creation
• Updates StatefulToolEnv.add_tool to use convert_func_to_oai_tool(filter_signature(...)), ensuring skipped args (incl. dict types) are absent from the exposed schema
• Maintains original function and bound method signatures; new tests cover dict-typed arg skipping and non-mutation of signatures

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