fix(utils): emit multi-type tool params as JSON array, not a comma-joined string

[anxkhn]

What

convert_function_to_tool serializes a tool parameter that has more than one type
(for example int | str) as the comma-joined string 'integer, string' instead of
the JSON-Schema array ['integer', 'string'].

Why this is a bug

The generated type string is not valid JSON Schema. The Ollama server parses a
parameter type that is a JSON string as a single type name, so 'integer, string'
is read as one (nonexistent) type and the multi-type constraint is silently dropped.
The array form is the shape the schema expects: Tool.Function.Parameters.Property.type
is Optional[Union[str, Sequence[str]]] (ollama/_types.py), and an array is already
used as the canonical multi-type input elsewhere in the tests
(tests/test_client.py, 'type': ['integer', 'number']).

There is also a non-determinism bug: types is built as a set, so the same
function could serialize to 'integer, string' on one run and 'string, integer'
on the next.

Fix

In ollama/_utils.py, sort the types set and emit:

• a single type as a bare string (unchanged behavior), and
• multiple types as a sorted list (a real JSON array).

Sorting also makes the output deterministic. The empty-types edge case (a
parameter typed only None) keeps its prior '' output via ''.join([]).

sorted_types = sorted(types)
schema['properties'][k] = {
  'description': parsed_docstring[k],
  'type': sorted_types if len(sorted_types) > 1 else ''.join(sorted_types),
}

Tests

Updated tests/test_utils.py::test_function_with_all_types so the multi-type
parameter (v: int | str | None on Python >= 3.10) is asserted to be a JSON array:

assert isinstance(tool['function']['parameters']['properties']['v']['type'], list)
assert tool['function']['parameters']['properties']['v']['type'] == ['integer', 'string']

This replaces the previous fragile string-parsing assertion (which stripped
brackets and split on commas). The new assertion fails on the old comma-joined
string and passes with the fix.

Verified locally:

• uv run pytest ollama tests -q -> 97 passed (doctests included)
• uvx hatch fmt --check -f (format) and uvx hatch fmt --check -l (lint) -> pass
• uv lock --check -> ok; uv export vs requirements.txt -> no diff

Single-type parameters (e.g. x: int -> 'integer') are unaffected.

[vaderollama]

LGTM — fixes a real bug where multi-type tool params (e.g. int | str) were serialized as the comma-joined string 'integer, string' instead of the JSON-Schema array ['integer', 'string']. The server parses a string type as a single type name, so the multi-type constraint was silently dropped. Using sorted() for determinism is a nice touch. Tests updated to assert the array format.

@ParthSareen — ready to merge.