fix: preserve function tool schema constraints

[weivwang]

Summary

Preserve JSON Schema constraints generated for Python function parameters when converting callables into Ollama tools.

convert_function_to_tool currently replaces each property schema with only type and description. That drops constraints such as array items and Literal enum values, so models are not told what array elements or allowed values a tool accepts.

This change keeps the generated property fields, removes the superseded anyOf, and then applies the existing normalized type and docstring description behavior.

Testing

• NO_PROXY=localhost,127.0.0.1 no_proxy=localhost,127.0.0.1 uv run --with pytest --with pytest-anyio --with pytest-httpserver pytest ollama tests -q (103 passed)
• uv run --with ruff ruff check ollama tests
• uv run --with ruff ruff format --check ollama tests
• git diff --check