Correct a drifted print queue instead of leaving it wrong

A queue was matched by NAME alone, so a bay whose printer had moved, or whose
queue was built on a driver the site has since replaced, looked converged and
printed to the wrong device. Absence was fixed; drift was not.

Set-ShopdbPrinters.ps1 now repoints a queue whose port does not match the
address ShopDB holds, and swaps a queue built on the wrong driver. Both are
things ShopDB is authoritative about: where the printer IS, and what drives it.

CORRECTED IN PLACE with Set-Printer, never removed and recreated. The queue keeps
its name, its sharing, its permissions, and whoever has it as their default keeps
it - which is what makes this safe to run every cycle on a live floor. There is
still no removal code path in this script at all.

Two guards, because a repair that breaks a working printer is worse than drift:
the driver is only swapped when the wanted one is actually staged, and
-WhatIfOnly reports both kinds of correction without making either.

Verified on Windows against a queue that had the right name, the wrong port, the
wrong driver AND was the logged-on user's default: both fields were corrected and
the queue was still the default afterwards. The earlier no-op guarantees were
re-run and still hold - nothing assigned changes nothing, and an assignment with
no default leaves the user's own default alone.

plugins/printers/client/Set-ShopdbPrinters.ps1

@@ -93,6 +93,61 @@ if ($wanted.Count -eq 0) {
 }
 Log "assigned: $($wanted.Count) printer(s)"
 
+function Ensure-Port([string]$address) {
+    $portname = 'IP_' + $address
+    if (-not (Get-PrinterPort -Name $portname -ErrorAction SilentlyContinue)) {
+        Add-PrinterPort -Name $portname -PrinterHostAddress $address -ErrorAction Stop
+        Log "port: $portname"
+    }
+    return $portname
+}
+
+function Repair-Queue($queue, [string]$address, [string]$drivername) {
+    $name = $queue.Name
+
+    # The address ShopDB holds is the truth about where the printer IS. A queue
+    # left pointing at the old address prints into the void, and looks fine.
+    if ($address) {
+        $wantedport = 'IP_' + $address
+        if ($queue.PortName -ne $wantedport) {
+            if ($WhatIfOnly) {
+                Log "WOULD repoint $name : $($queue.PortName) -> $wantedport"
+            } else {
+                try {
+                    $portname = Ensure-Port $address
+                    Set-Printer -Name $name -PortName $portname -ErrorAction Stop
+                    Log "repointed $name : $($queue.PortName) -> $portname"
+                } catch {
+                    Log "ERROR repointing ${name}: $($_.Exception.Message)"
+                }
+            }
+        }
+    }
+
+    # A queue built on a driver the site has moved off keeps using it forever.
+    # Only corrected when the wanted driver is actually staged - swapping a queue
+    # onto a driver that is not installed would break a working printer.
+    if ($drivername -and $queue.DriverName -ne $drivername) {
+        if (-not (Get-PrinterDriver -Name $drivername -ErrorAction SilentlyContinue)) {
+            Log "SKIP driver fix for $name : '$drivername' is not staged"
+        } elseif ($WhatIfOnly) {
+            Log "WOULD re-driver $name : $($queue.DriverName) -> $drivername"
+        } else {
+            try {
+                Set-Printer -Name $name -DriverName $drivername -ErrorAction Stop
+                Log "re-drivered $name : $($queue.DriverName) -> $drivername"
+            } catch {
+                Log "ERROR re-drivering ${name}: $($_.Exception.Message)"
+            }
+        }
+    }
+
+    if ($queue.PortName -eq ('IP_' + $address) -and
+        ($drivername -eq '' -or $queue.DriverName -eq $drivername)) {
+        Log "present: $name"
+    }
+}
+
 $existing = @{}
 foreach ($queue in (Get-Printer -ErrorAction SilentlyContinue)) {
     $existing[$queue.Name] = $queue
@@ -104,19 +159,28 @@ foreach ($printer in $wanted) {
     if (-not $name) { continue }
     if ($printer.printerid -eq $defaultid) { $defaultname = $name }
 
+    $address = $printer.hostname
+    if (-not $address) { $address = $printer.ipaddress }
+    $drivername = $printer.drivername
+
     if ($existing.ContainsKey($name)) {
-        Log "present: $name"
+        # A queue with the right NAME can still be wrong: pointing at a printer
+        # that has moved, or built on a driver that has since been replaced.
+        # Absence used to be the only thing fixed, so a bay with a stale queue
+        # looked converged and printed to the wrong device.
+        #
+        # Corrected IN PLACE with Set-Printer, never removed and recreated: the
+        # queue keeps its name, its sharing, its permissions, and whoever has it
+        # as their default keeps it.
+        Repair-Queue $existing[$name] $address $drivername
         continue
     }
 
-    $address = $printer.hostname
-    if (-not $address) { $address = $printer.ipaddress }
     if (-not $address) {
         Log "SKIP $name : no hostname or IP to point a port at"
         continue
     }
 
-    $drivername = $printer.drivername
     if (-not $drivername) {
         Log "SKIP $name : ShopDB has no driver name for it"
         continue
@@ -132,12 +196,8 @@ foreach ($printer in $wanted) {
         continue
     }
 
-    $portname = 'IP_' + $address
     try {
-        if (-not (Get-PrinterPort -Name $portname -ErrorAction SilentlyContinue)) {
-            Add-PrinterPort -Name $portname -PrinterHostAddress $address -ErrorAction Stop
-            Log "port: $portname"
-        }
+        $portname = Ensure-Port $address
         Add-Printer -Name $name -DriverName $drivername -PortName $portname -ErrorAction Stop
         Log "created: $name -> $address ($drivername)"
     } catch {