Mock OA from past questions

Part of oahelper-mcp by Sirjan Singh.

1. Build the paper

1. oahelper_offline(company). If nothing is saved, run oahelper_sync(company) until it stops saying NOT DONE (or about 40 live requests, whichever comes first).
2. Read library/<co>/index.md and the newest 2 or 3 set files. Copy the real format: number of coding vs MCQ questions, and the time limit if the sets or interview write-ups state one. If no time limit is known, use 90 minutes for 2 to 3 coding questions and 1 minute per MCQ, and say it is an assumption.
3. Pick questions the user has not attempted (check library/_progress.md if it exists). Prefer sets from the last 12 months. Mix difficulties like the real sets do.
4. Never show answers, official solutions or MCQ keys while the mock is running.

2. Run it