Test bounded real-time simulation

[lbussy]

Related to WsprryPi/WsprryPi#400.

Summary

• add a dedicated real-time simulated-backend contract test
• distinguish real-time waiting from accelerated virtual time with a broad lower bound
• verify deterministic logical trace ordering and same-instance state reset
• verify an in-progress real-time wait can be interrupted promptly
• expose the test through a focused Make target

Bounds

• successful execution: two 40 ms waits, at least 60 ms and under 4 seconds
• cancellation: interrupt one 2-second wait after 30 ms and require return under 1.5 seconds
• parent CI adds a hard 5-second process timeout

These are behavioral guardrails, not scheduler precision or jitter assertions.

Validation

• focused test passed repeatedly on Debian ARM64
• existing simulated-backend test passed
• transmission-controller contract test passed
• focused execution passed under strace
• parent hardware-access audit reported no prohibited transmitter access
• git diff --check

No hardware, GPIO, I2C, MMIO, mailbox, DMA, device-node, service, installation, sudo, or RF operation was used.