Improve LSN gap check

RestoreScript.ps1

@@ -577,7 +577,24 @@ function Print-BackupSummary {
             Write-Host "  Point-in-Time Range: $(([datetime]$firstLog.BackupStartDate).ToString([System.Globalization.CultureInfo]::CurrentCulture)) to $(([datetime]$lastLog.BackupFinishDate).ToString([System.Globalization.CultureInfo]::CurrentCulture))"
             Write-Host "  LSN Range: $($firstLog.FirstLSN) - $($lastLog.LastLSN)"
 
-            # Check for gaps
+            # Check that the first LOG connects to the most recent FULL (or DIFF if one exists).
+            $baseLastLsn = $null
+            $baseLabel = $null
+            if ($Headers.ContainsKey('DIFF') -and $Headers['DIFF'].Count -gt 0) {
+                $latestDiff = @($Headers['DIFF'] | Sort-Object { $_.Key })[-1]
+                $dh = @($latestDiff.Header)[0]
+                if ($dh) { $baseLastLsn = $dh.LastLSN; $baseLabel = "DIFF $($latestDiff.Key)" }
+            }
+            if (-not $baseLastLsn -and $Headers.ContainsKey('FULL') -and $Headers['FULL'].Count -gt 0) {
+                $latestFull = @($Headers['FULL'] | Sort-Object { $_.Key })[-1]
+                $fh = @($latestFull.Header)[0]
+                if ($fh) { $baseLastLsn = $fh.LastLSN; $baseLabel = "FULL $($latestFull.Key)" }
+            }
+            if ($baseLastLsn -and [decimal]$firstLog.FirstLSN -gt [decimal]$baseLastLsn) {
+                Write-Host "  *** LSN GAP: first LOG (LSN $($firstLog.FirstLSN)) does not connect to $baseLabel (ends LSN $baseLastLsn) — point-in-time restore will fail ***"
+            }
+
+            # Check for gaps within the LOG sequence
             $gaps = @()
             for ($i = 1; $i -lt $logItems.Count; $i++) {
                 $prevHeader = @($logItems[$i-1].Header)[0]