canvas-scan

This skill should be used when scanning Canvas for pending assignments and producing an approval-gated plan. Invoked manually when the user says "check canvas", "scan canvas", "what's due", "do my homework", "/canvas-scan". Reads courses.yaml, queries Canvas for assignments due in the configured pending window, buckets them by urgency, renders a plan table, writes runs/<today>/plan.json, and STOPS. Does NOT dispatch…