add periodic snapshot reset

deploy/arm64-installer/.env.example

@@ -42,6 +42,12 @@ CLEAN_TMP_AFTER_RUN=0
 OUTPUT_COMPACT_REPORT=1
 ALLOW_RSYNC_MIRROR_REUSE=1
 FAILURE_SNAPSHOT_RESET=1
+# Periodic snapshot reset of active state DB.
+# 0: keep existing behavior.
+# 1: after one successful snapshot, allow at most N successful delta runs;
+#    the next run is forced to snapshot and active state/db is rebuilt from empty.
+PERIODIC_SNAPSHOT_RESET=0
+PERIODIC_SNAPSHOT_MAX_DELTAS=100
 DB_STATS_EXACT_EVERY=0
 
 # Validation and performance options aligned with current optimized soak defaults.