Adds AIRK-GOV001 for supported instruction files that do not show a clear scope or authority boundary.

Summary:

• adds a conservative missing scope/authority governance finding
• keeps the rule read-only and path-local to supported instruction files
• adds unit and CLI JSON coverage
• isolates existing diagnostic fixtures so prior rule smokes remain stable

Boundary:

• does not decide authority hierarchy automatically
• does not resolve instruction conflicts
• does not rewrite or normalize instruction files
• does not touch README or release artifacts

Verification:

• ./scripts/check.sh
• CLI JSON smoke for AIRK-GOV001
• CLI JSON smoke for AIRK-GOV002
• CLI JSON smoke for AIRK-GOV003
• CLI JSON smoke for AIRK-GOV006
• clean fixture smoke
• isolated build and wheel install smoke