observability

This skill is the thinking process for adding it. Not "add logs everywhere" — add the right signals at the right decision points.

Invocation points:

• Building auto-mode-style code (loops, dispatch, guards, retries)
• Adding a background job, watcher, or scheduled task
• Writing a server or long-running process
• Refactoring a subsystem that has been hard to debug
• Addressing a production bug where "we had no visibility" surfaced

<core_principle> LOG DECISIONS, NOT ACTIVITY. "Entering function X" is noise. "Dispatched unit slice/S02 after guard check passed because status=pending" is signal. Every log line should answer a question a future debugger will ask.