advice Directory Reference

Files
	advice.hpp
	The advice file (design doc 17, issue #26): typed hints for the router, written by a person, a script or a language model, and read by the engine like any other input.
	advisor.hpp
	The advisor protocol (design doc 17 §5): an advisor is any executable that reads a stuck report (JSON) on stdin and writes an advice file (JSON) on stdout.
	stuck_report.hpp
	The stuck report (design doc 17 §3, issue #26 stage 0): what failed and why, as JSON that an advisor (a person, a script or a model) can act on.