feat(audit): archive retention and superseded stale-archive cleanup (ScadaBridge#109)

Owner decisions recorded: the archive destination stays a directory/UNC
(no object-storage client; share + permissions named at enablement),
parquet-tools-only reading (no re-import), unsigned like the chain (#107).

AuditLog:Archive:RetentionDays (default 0 = never delete; else must exceed
AuditLog:RetentionDays, counted from the archived month's end) and
DeleteSupersededStaleArchives (default true) run after every purge tick.
A retried purge's stale Archived archive is deleted only when a later,
verifying, Purged archive of the same partition provably holds every row:
same prior anchor and the stale chain-end hash at its chain-end sequence
(row or tombstone), every unchained row present by EventId; otherwise it is
reported KeptStale. A sole copy left at Archived is never touched. Deletion
removes only the archive name's own three files in its folder, manifest
first, never a manifest-supplied path. `audit archive cleanup [--dry-run]`
= CleanupAuditArchives (Administrator).

AuditLogArchiveCleanupTests (MSSQL) cover retried purge, kept stale copy,
sole copy, retention and the path guard; each safety rule mutation-checked.
Follow-ups filed: #113, #114, #115.

Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV

src/ZB.MOM.WW.ScadaBridge.Commons/Messages/Management/AuditLogCommands.cs

@@ -57,3 +57,12 @@ public record ListAuditArchivesCommand;
 /// </summary>
 /// <param name="Name">The archive name, as <c>audit archive list</c> reports it.</param>
 public record VerifyAuditArchiveCommand(string Name);
+
+/// <summary>
+/// Runs the AuditLog archive cleanup (ScadaBridge#109) now: deletes superseded stale archives
+/// a retried purge left behind and archives past <c>AuditLog:Archive:RetentionDays</c> — or,
+/// with <paramref name="DryRun"/>, only reports what it would delete. The purge actor runs the
+/// same pass after every purge tick. Administrator only (it deletes files).
+/// </summary>
+/// <param name="DryRun">Report only; delete nothing.</param>
+public record CleanupAuditArchivesCommand(bool DryRun);