Add Granite tool parser

[jonpspri]

Summary

• Add a Granite-specific tool parser for <tool_call> JSON payloads that tolerates extra trailing braces.
• Keep the generic JSON tool parser strict while allowing Granite models to opt in via tool_parser_type: granite.
• Add parser tests covering valid JSON, repeated trailing braces, nested arguments, and invalid trailing junk.

Tests

• PYTHONPATH=. uv run pytest tests/test_tool_parsing.py