TOMATO-58: Implement adapter registry and production scaffold driver path

[cracketus]

Summary

• add hardware adapter registry/loader APIs and strict dispatch-result validation
• add production-intended production_scaffold adapter with explicit TODO boundary for real transport wiring
• wire scripts/simulate_day.py to support --executor-backend hardware + --hardware-driver
• keep backward-compatible deterministic paths for mock and hardware_stub
• update Stage 5 docs in README/AGENTS/PLANNED_FEATURES
• add test coverage for registry, executor notes, and CLI/run driver selection

Testing

• pytest -q --no-cov tests/executor/test_hardware_adapter.py tests/executor/test_hardware_executor.py tests/scripts/test_simulate_day_cli.py tests/scripts/test_simulate_day_run.py
• result: 19 passed

Closes #70