The refreshed provider table said 12 embedders; EmbedderFactory registers 11.
The other three rows were right, so the table drifted silently again inside the
commit that was fixing it drifting.
Add tests/test_agents_md_provider_counts.py, which parses the AGENTS.md provider
table and asserts each documented count equals len(<Factory>.provider_to_class).
Verified it fails on the 12 and passes on 11.
kartik-mem0