test: make physical MobileCore QA fail closed

[Harzva]

Summary

• require model switching, background recovery, and at least 15 minutes of thermal workload for counted physical-device acceptance
• verify airplane mode enable/restore instead of recording a hard-coded offline result
• require an accepted RUNNING_LOW trim with MobileCore still model-ready
• derive multimodal and thermal offline evidence from observed device state
• document the strict gates and expand deterministic host coverage

Verification

• python3 -m py_compile scripts/run_mobilecore_dual_app_qa.py scripts/test_run_mobilecore_dual_app_qa.py
• python3 -m unittest scripts/test_run_mobilecore_dual_app_qa.py (16 tests)
• strict physical-device run against an emulator fails before APK installation
• semgrep scan --config p/secrets --error --quiet on changed files
• added-line credential/private-path scan: 0 findings

Remaining acceptance

A passing manifest still requires a connected physical Android device, a second compatible local model, and the full 30-task/thermal run. This PR deliberately does not claim that physical-device evidence.