Feature/v0.4.0/structured output

[mavdol]

Summary

This PR introduces significant improvements to task execution and observability:

1. Structured Task Response Envelope

Tasks now return a detailed JSON envelope containing execution metadata alongside results. This provides better visibility into task performance and error handling.

Example:

@task(name="data_processor")
async def process_data():
    return {"status": "processed", "count": 42}

@task(name="main")
async def main():
    response = await process_data()
    return response

Response format:

{
  "success": true,
  "result": {
    "status": "processed",
    "count": 42
  },
  "error": null,
  "execution": {
    "task_name": "data_processor",
    "duration_ms": 1523,
    "retries": 0,
    "fuel_consumed": 45000
  }
}

Fields:

• success: Boolean indicating task completion status
• result: The actual return value from the task (only present on success)
• error: Error details if the task failed (type and message)
• execution: Metadata about the task execution (name, duration, retry count, fuel consumption)

2. Enhanced Logging with --verbose

Improved error messages with consistent formatting for better debugging:

[test_async_timeout] timeout after 5000ms
[test_immediate_fuel_exhaustion] fuel exhausted during execution
[test_ram_limit] memory limit exceeded: minimum 202 pages required
[my_task] execution failed: division by zero

Error categories:

• Timeout errors: Clear indication when tasks exceed time limits
• Resource exhaustion: Memory and fuel limit violations
• Execution errors: Runtime errors with descriptive messages

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⚠️ Breaking Changes: Task return values are now wrapped in the JSON envelope structure. Existing code may need to access response.result instead of using response directly.