Revise mistakes

Part of oahelper-mcp by Sirjan Singh.

The log is library/_progress.md, a table written by oa-mock, mcq-drill and solve-coach:

| date | company | ref | title | topic | result |

If it does not exist, say there is nothing to revise yet and suggest mcq-drill or oa-mock to start one.

1. Pick what is due

Take the latest row per ref. Due when: