baselineExistingInstall, healInitialSchemaDrift, and healRenamedColumns
existed only because of pre-squash intermediate states: dev DBs drifted
against drizzle-kit's assumed 0000 baseline, or carried pre-rename
columns from the old manual migration system. Under a single squashed
baseline there are no intermediate states to drift against, and these
functions are unreachable.
initDatabase() is now: pragmas -> drizzle() -> migrate() -> ensureDefaults().
ensureDefaults stays (idempotent startup seeding for settings row, worker
ID, first-admin promotion).
Refs backlog #31 Phase 2.