Allow Timestamp in dontScanBefore

Now storing UTC timestamp in the dontScanBefore field.

salt/soc/defaults.yaml

@@ -1539,6 +1539,7 @@ soc:
             DetectionEngineer: gemma@SOAI
           useMemory: true
           useMemoryScanner: false
+          dontScanBefore: ""
           memoryScanIntervalSeconds: 300
           memoryProximityThreshold: 0.8
           messageProximityThreshold: 0.5

salt/soc/soc_soc.yaml

@@ -853,6 +853,12 @@ soc:
             description: Enables the memory scanner for automatic memory extraction from historical sessions.
             global: True
             forcedType: bool
+          dontScanBefore:
+            description: A date specifying how far back to scan for memories. Must be in YYYY-MM-DD format.
+            regex: "^(\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(\.\d+)?Z)?$"
+            regexFailureMessage: Expecting date in RFC3339 format (2026-08-31T22:05:48Z)
+            global: True
+            advanced: True
           memoryScanIntervalSeconds:
             description: How long to wait in seconds between attempts to scan sessions for new memories.
             global: True