Function planRetention

planRetention(
    dir: string,
    policy?: RetentionPolicy,
    options?: {
        classify?: (file: string) => "snapshot" | "unknown" | "active" | "log";
    },
): RetentionDecision
Plan retention for a directory of room logs/snapshots.

Naming convention used by FilePersistence:
- <roomId>.log ← active log (never deleted by this fn)
- <roomId>.log.<isoStamp> ← rotated logs (auditable)
- <roomId>.snap.<isoStamp> ← periodic snapshots (kept longer)
Plus SnapshotWorker's real output, which is what actually lands on disk today (FilePersistence compacts its log in place and never rotates it):
- <roomId>.<isoStamp>.ifcx ← periodic snapshots, classified snapshot
Tools shipping their own naming convention can pass a custom matcher via the classify option.
Parameters
- dir: string
- Optionalpolicy: RetentionPolicy
- Optionaloptions: { classify?: (file: string) => "snapshot" | "unknown" | "active" | "log" }
Returns RetentionDecision