fix: implement raw JSON extraction fallback

[Gavin2318]

Repro:
poetry run python src/main.py --tickers NVDA
Select Charlie Munger
Select DeepSeek R1

when the code runs to line 124, src/agents/charlie_munger.py

        munger_output = generate_munger_output(
            ticker=ticker, 
            analysis_data=analysis_data,
            state=state,
            agent_id=agent_id,
        )

then line 55, src/utils/llm.py

result = llm.invoke(prompt)

The LLM output message below:

{
  "signal": "neutral",
  "confidence": 55.0,
  "reasoning": "The business showcases a formidable moat with exceptional ROIC (>15% in 8/10 periods) and pricing power (63% gross margins), demonstrating classic competitive advantages through intellectual property and scale. However, applying the margin of safety principle from value investing reveals fatal valuation issues: a mere 0.5% FCF yield and 92% premium to reasonable value mean we're paying a foolish price for future growth. Furthermore, inverting the problem highlights critical risks – revenue and margin volatility (49.6% growth with high fluctuations, 34.1% margins with 11.2% volatility) violates our requirement for predictable cash flows, while moderate share dilution erodes per-share value. Management's conservative debt (D/E 0.13) and cash conversion (FCF/NI 1.05) are praiseworthy, but cannot offset the valuation excess. As I often say, 'The price you pay determines your rate of return' – here, we abstain despite the quality."
}

then in line 59, src/utils/llm.py, it outputs None, since it didn't find ```json

parsed_result = extract_json_from_response(result.content)

To fix this issue, I add code below to try to extract json content directly when three is no ```json in the LLM output

return json.loads(content) inside function extract_json_from_response

def extract_json_from_response(content: str) -> dict | None:
    """Extracts JSON from markdown-formatted response."""
    try:
        json_start = content.find("```json")
        if json_start != -1:
            json_text = content[json_start + 7 :]  # Skip past ```json
            json_end = json_text.find("```")
            if json_end != -1:
                json_text = json_text[:json_end].strip()
                return json.loads(json_text)
        # Try to extract json directly
        return json.loads(content)
    except Exception as e:
        print(f"Error extracting JSON from response: {e}")
    return None

[virattt]

I like it, will take a closer look