- Added repair_broken_tool_calls() function that handles common hallucinated formats:
  - <tool><tool_name><param>value</param></tool> (missing closing tag)
  - <tool><tool_name><param>value</param></tool_name></tool>
  - Simple format: <tool><list_files><path>.</path><recursive>true</recursive></tool>

- Integrated repair into:
  - QwenParser.parse() - primary parser for Qwen models
  - ToolCallParser.extract_tool_calls() - fallback parser
  - ModelParserAdapter.extract_tool_calls() - adapter wrapper

The repair converts broken XML format to valid JSON:
<tool><list_files><path>.</path><recursive>true</recursive></tool>
becomes:
<tool>{"name": "list_files", "arguments": {"path": ".", "recursive": true}}</tool>

This fixes tool call extraction when the model hallucinates broken XML tags.