ADK Agent fails to start due to `No root_agent found` error

The ADK agent fails to start with a `No root_agent found` error, even after ensuring the file structure is correct and the agent is exposed in a top-level `agent.py`. This issue persists after refactoring the project from Poetry to a standard Python `venv` with `requirements.txt`.

**Error:**
```
ValueError: No root_agent found for '1-basic-agent'. Searched in '1-basic-agent.agent.root_agent', '1-basic-agent.root_agent'. Ensure '/Users/jjespinoza/Documents/PersonalGitHub/agent-development-kit-masterclass/1-basic-agent' is structured correctly, an .env file can be loaded if present, and a root_agent is exposed.
```

**To Reproduce:**
1. Clone the repository.
2. Create and activate a virtual environment.
3. Install dependencies from `requirements.txt`.
4. Run `adk web` from within the `1-basic-agent` directory.

The server fails to start and logs the error above.