Address PR #7 review thread: lifecycle docs + startup logging behavior

[Copilot]

This update resolves all actionable comments from review thread pullrequestreview-4630653075, with scope limited to the requested thread. Changes align lifecycle documentation with actual engine behavior and remove import-time INFO log noise introduced by default engine startup.

• Lifecycle contract docs aligned with runtime behavior

  • EngineNotStartedError docstring now explicitly covers both trigger() and trigger_type().
  • AutomationEngine.stop() docstring now states that stop deregisters components, so restart requires re-registration.

• Startup logging adjusted for library ergonomics

  • AutomationEngine.start() startup message moved from INFO to DEBUG to avoid INFO output during module import (default_engine.start() side effect).

• Regression coverage for log-level expectation

  • Added a focused test asserting startup emits the expected DEBUG log record.

# before
logger.info("AutomationEngine started")

# after
logger.debug("AutomationEngine started")