Add changeset for the local v1→v2 upgrade hardening (#983)

Author: RhysSullivan

.changeset/local-v1-v2-ledger.md

@@ -0,0 +1,15 @@
+---
+"executor": patch
+---
+
+**Hardened the local v1→v2 database upgrade**
+
+Upgrading a local database created by an older (v1) release is now resilient to
+interrupted or partially-written upgrade state:
+
+- The one-time upgrade is recorded in the migration ledger, so it is never
+  re-attempted on later boots. Databases that have already upgraded are detected
+  from the ledger and skip the upgrade path entirely.
+- Replaying the legacy schema now tolerates a missing or truncated migration
+  journal instead of failing to start, so a database left in a half-written
+  state from a previous crash boots cleanly.