feat: improve consistency checks and error reporting

Scripts/Helpers/Import-ConfigToParams.ps1

@@ -31,6 +31,11 @@ function Import-ConfigToParams {
         throw "Failed to read config file: $resolvedConfigPath"
     }
 
+    $consistencyError = Test-ConfigConsistency -Config $configJson
+    if ($consistencyError) {
+        throw "Invalid config file '$resolvedConfigPath': $consistencyError"
+    }
+
     $importedItems = 0
 
     if ($configJson.Apps) {

Scripts/Helpers/Test-ConfigConsistency.ps1

@@ -0,0 +1,56 @@
+<#
+    .SYNOPSIS
+        Validates that a configuration file is structurally consistent before it is applied.
+
+    .DESCRIPTION
+        Returns $null when the configuration is valid, otherwise a string describing the
+        first problem found. Used by both the CLI and GUI import paths to reject invalid
+        configs before any settings are applied.
+
+    .OUTPUTS
+        System.String. $null when valid, otherwise an error message.
+#>
+function Test-ConfigConsistency {
+    param($Config)
+
+    if (-not $Config) {
+        return 'Configuration is empty or could not be read.'
+    }
+
+    if (-not $Config.Version) {
+        return 'Configuration is missing a Version field.'
+    }
+
+    if (-not $Config.Apps -and -not $Config.Tweaks -and -not $Config.Deployment) {
+        return 'The configuration file contains no importable data.'
+    }
+
+    $lookup = @{}
+    foreach ($setting in @($Config.Deployment)) {
+        if ($setting -and $setting.Name) {
+            $lookup[$setting.Name] = $setting.Value
+        }
+    }
+
+    $hasScope = $lookup.ContainsKey('AppRemovalScopeIndex')
+    $hasUser = $lookup.ContainsKey('UserSelectionIndex')
+
+    # "Current user only" (index 1) is only valid together with "Current User" (index 0)
+    if ($hasScope -and [int]$lookup['AppRemovalScopeIndex'] -eq 1) {
+        if (-not $hasUser -or [int]$lookup['UserSelectionIndex'] -ne 0) {
+            return "App removal scope 'Current user only' (AppRemovalScopeIndex 1) requires the deployment target 'Current User' (UserSelectionIndex 0)."
+        }
+    }
+
+    # "Target user only" (index 2) is only valid together with "Other User" (index 1)
+    if ($hasScope -and [int]$lookup['AppRemovalScopeIndex'] -eq 2) {
+        if (-not $hasUser -or [int]$lookup['UserSelectionIndex'] -ne 1) {
+            return "App removal scope 'Target user only' (AppRemovalScopeIndex 2) requires the deployment target 'Other User' (UserSelectionIndex 1)."
+        }
+        if (-not $lookup.ContainsKey('OtherUsername') -or [string]::IsNullOrWhiteSpace("$($lookup['OtherUsername'])")) {
+            return "App removal scope 'Target user only' (AppRemovalScopeIndex 2) requires an 'OtherUsername' value."
+        }
+    }
+
+    return $null
+}