TOMATO-60: Add deterministic retry policy and backoff scheduling

[cracketus]

Summary

• add configurable deterministic retry policy (RetryPolicyConfig) for hardware dispatch failures
• extend hardware dispatch result metadata with retryability/error class and add deterministic laky_stub driver for runtime retry validation
• integrate retry/backoff scheduling into HardwareExecutor with deterministic retry timestamps
• emit retry scheduling events into executor_log.jsonl for observability
• enforce fail-fast non-retryable/class-blocked paths with clear reason codes
• add --force-water-action runtime helper to exercise execution/retry path in deterministic simulation tests
• update Stage 5 docs in README/AGENTS/PLANNED_FEATURES

Testing

• pytest -q --no-cov tests/executor/test_retry_policy.py tests/executor/test_hardware_executor.py tests/scripts/test_simulate_day_run.py
• pytest -q --no-cov tests/scripts/test_simulate_day_cli.py
• result: 20 passed

Closes #72