feat: support headless session execution via --config flag

[rosspeili]

Problem Statement

Currently, every Rooms session requires manual interaction with the CLI wizard. This prevents the framework from being used in automated simulations, CI/CD pipelines, or as part of larger scripted workflows where a human is not present to answer prompts.

Proposed Solution

1. Add a new --config <file_path> argument to cli.py (e.g., using argparse or typer).
2. Implement a loading mechanism that can parse a SessionConfig directly from a YAML or JSON file.
3. If the --config flag is present, the application should bypass the interactive wizard entirely, initialize the session with the provided file, and begin execution immediately.

Alternatives Considered

None. Headless execution is a standard requirement for framework automation.

Priority

Medium 🟡

Additional Context

This feature depends on the programmatic Rooms API refactor. It serves as the primary interface for non-interactive environments.