Update lesson 1 to have only 1 grammar topic

Update to lesson v2: remove old lesson, fix cache parsing

Merge remote-tracking branch 'origin/main' into orchestration-implementation

Restore ContentAgent (Agent 3) with RAG integration

Add simplified lesson 1 v2

Clean up docs

Fix Agent 3 RAG schema mismatch - remove 'correct' field

Complete Agent 3 evaluation infrastructure and identify RAG schema issue

Improve on RAG content to have right size

Fix inconsistencies

Fix inconsistencies

Create RAG DB content for lesson 1 and reusable exercises