vault-lifecycle-four-lane-not-three-lane

The Vault Brain hygiene operates on four distinct lanes, not three: (1) real-time cascade on vault_submit_* calls, (2) transcript auto-capture at session close via conversation-flush.py, (3) nightly cron for hot cache refresh (vault-hot-cache.sh, zero API cost), (4) weekly NOVA structural sweep for broken links and frontmatter. Documenting it as three-lane omits the transcript lane which handles the most session intelligence.