fix: strip hallucinated <tool_result> blocks from ReACT message history

[octo-patch]

Fixes #529

Problem

The ReACT section generation loop in report_agent.py appended the raw LLM response to message history including any <tool_result> blocks the LLM may have fabricated in its own reply. This caused subsequent iterations to treat invented data as authoritative, producing reports with completely fabricated usernames, quotes, and statistics.

Solution

Added a _strip_fake_tool_results() static method to ReportAgent that removes any <tool_result>...</tool_result> blocks from the LLM response before it is recorded in message history:

@staticmethod
def _strip_fake_tool_results(response: str) -> str:
    cleaned = re.sub(r'<tool_result>.*?</tool_result>', '', response, flags=re.DOTALL)
    cleaned = re.sub(r'\n{3,}', '\n\n', cleaned)
    return cleaned.strip()

The call site in the tool execution path (previously line ~1456) now passes the cleaned response to messages.append() instead of the raw response, while the real tool result is still injected via REACT_OBSERVATION_TEMPLATE as before.

Testing

• The static method can be unit-tested by passing a string containing fabricated <tool_result> blocks and verifying they are removed while the <tool_call> block is preserved.
• Manually verified that the regex correctly strips only <tool_result> blocks and collapses resulting extra blank lines.