fix: harden OpenRouter target runs

[zeuzmakessoftware]

Summary:

• resolve OpenRouter PydanticAI profiles through the native OpenRouter provider and require the configured API key
• wrap malformed 200/JSON provider responses with actionable context
• require generated target agents to bound API timeouts/retries and update the GPQA reference agent

Tests:

• python -m pytest tests/ -v
• ruff check sia/ tests/
• ruff format --check sia/ tests/
• ty check sia/ (passes with existing optional google.generativeai unresolved-import warning)