One source of truth for agent instructions

Every assistant wants its own rules file. Copy the same text into nine places and the copies drift within weeks; put pointers in the wrong places and a tool silently gets no instructions at all. The fix is one canonical file and thin references at the paths each tool actually loads.

Audit first

python scripts/check_agent_files.py [repo_dir]          # report
python scripts/check_agent_files.py [repo_dir] --strict # exit 1 on problems (CI)

It is read-only. It lists every instruction file a known tool loads and classifies each one: