Merge branch 'worktree-agent-a3b474b485c0288de' into arch-review-remediation

src/ZB.MOM.WW.ScadaBridge.ConfigurationDatabase/Configurations/AuditLogEntityTypeConfiguration.cs

@@ -172,15 +172,18 @@ public class AuditLogEntityTypeConfiguration : IEntityTypeConfiguration<AuditLog
         // ── Keys + indexes ───────────────────────────────────────────────────
 
         // Composite PK includes OccurredAtUtc — required by the monthly partition scheme
-        // (ps_AuditLog_Month) so the clustered key is partition-aligned. EventId still
-        // needs to be globally unique for InsertIfNotExistsAsync idempotency, so a
-        // separate (non-aligned) unique index is declared on EventId alone.
+        // (ps_AuditLog_Month) so the clustered key is partition-aligned. It is ALSO the
+        // only uniqueness enforcement the ingest path needs: EventId is a GUID minted
+        // once at the emitting site and never re-stamped, so a given EventId always
+        // arrives with the same OccurredAtUtc and can only ever land in one partition.
+        // Uniqueness of the pair is therefore uniqueness of EventId in practice, and the
+        // idempotency probe (WHERE EventId = @id) still seeks the clustered key's leading
+        // column. The predecessor non-aligned UX_AuditLog_EventId on [PRIMARY] was
+        // dropped by AlignAuditLogEventIdUniqueness — it existed only to give
+        // single-column uniqueness and its non-alignment forced an offline drop/rebuild
+        // around every partition-switch purge.
         builder.HasKey(e => new { e.EventId, e.OccurredAtUtc });
 
-        builder.HasIndex(e => e.EventId)
-            .IsUnique()
-            .HasDatabaseName("UX_AuditLog_EventId");
-
         // Index names are locked for reconciliation/migration discoverability. The
         // column SETS migrate to the canonical/computed shape (alog.md §4 semantics
         // preserved): Channel→Category, Site/Node/Execution/ParentExecution now read