CLAUDE.md updates:
- new src/second_brain/embeddings/ entry in the project layout
- setup section now lists the postgres-superuser bootstrap (CREATE SCHEMA
AUTHORIZATION lovebug) and the alembic step
- env var table now covers SECOND_BRAIN_DATABASE_URL, OLLAMA_URL,
EMBEDDING_MODEL, and the pool sizing knobs
- conventions section gained five new gotchas (the lovebug CREATE gap,
public.embeddings ownership, best-effort embedding, etc.)
postgres-migration-planning.md flipped from "planning questions" to a
"what shipped" runbook — locked decisions table, operator setup steps,
known gotchas, and the next-iteration backlog.
