Atomically update all 6 Fluent learner databases (learner-profile, progress, mistakes, mastery, spaced-repetition, session-log) at session end by calling .claude/hooks/update-db.py with a single JSON payload. Use at the end of every practice session — fluent-writing, fluent-vocab, fluent-speaking, fluent-reading, fluent-review, fluent-learn — to persist the session's errors, review results, new vocabulary, and session metadata.