Develop Multi-Process Test Framework

Description

A custom testing framework will be built to validate complex, multi-device distributed scenarios directly within the Rust test suite. It orchestrates multiple cargo test subprocesses, each assuming a different device "role," to simulate real-world P2P interactions like pairing and file transfers.

Implementation Notes

• The core runner will be implemented in src/test_framework/runner.rs.
• Tests like device_pairing_test.rs and cross_device_copy_test.rs use this framework by defining distinct, #[ignore]-ed test functions for each role (e.g., alice_pairing_scenario, bob_pairing_scenario).
• The main test function acts as an orchestrator, spawning the subprocesses and coordinating their interaction using the filesystem for signaling.

Acceptance Criteria

• The framework can spawn multiple, isolated cargo test subprocesses.
• Each subprocess can be assigned a unique role and data directory via environment variables.
• The framework can coordinate and validate the outcomes of distributed tests (e.g., successful pairing).