Event migration runbook (sub-calendar v1) — moved

The sub-calendar v1 cutover migration (legacy event collection to the calendar-owned schema) shipped in releases up to v1.0.310. The migration code and this runbook were removed from later releases once Compass-operated production and staging completed the cutover (2026-07-15).

If your install still runs the pre-cutover event schema (you have never performed the write-pause-and-rename cutover, or mongosh shows no event_legacy_v1 collection and your app version predates v1.0.236):

1. Upgrade to v1.0.310 first — do not jump straight to a later release.
2. Follow that version's event migration runbook and the cutover section of its backup & restore guide in full.
3. Once the cutover is verified, upgrade to the latest release as a normal upgrade and run any remaining pending migrations.

If your install already cut over (or was first installed after v1.0.236), nothing here applies — upgrade normally.