Add try-except for json.JSONDecodeError in parse_agent_tasks() to
gracefully handle malformed JSON from LLM responses (e.g. Gemini 2.5
Flash via OpenRouter). Returns empty list on parse failure, which
triggers the existing retry mechanism in make_plan().
Add test suite for parse_agent_tasks() covering valid JSON, malformed
JSON, truncated JSON, and invalid agent name cases.
