feat: add standalone diagnostic script for installed plugin

Checks the installed manifest at App_Data\Plugins for Features array,
validates CategoryTypeName, scans Disco logs for plugin-related entries,
and shows file timestamps for the installed DLL.

Diagnose-InstalledPlugin.ps1

@@ -0,0 +1,107 @@
+# Diagnose-InstalledPlugin.ps1
+# Run this on the Disco server to check if the installed plugin has UIExtension features
+#
+# Usage:
+#   .\Diagnose-InstalledPlugin.ps1
+#   .\Diagnose-InstalledPlugin.ps1 -DiscoPath "D:\Disco\WebApp"
+
+param(
+    [string]$DiscoPath = "C:\Program Files\Disco\WebApp"
+)
+
+$PluginName = "Disco.Plugins.ADCompare"
+$pluginDir = Join-Path $DiscoPath "App_Data\Plugins\$PluginName"
+
+Write-Host "=== Installed Plugin Diagnostics ===" -ForegroundColor Cyan
+Write-Host "Checking: $pluginDir" -ForegroundColor Gray
+
+if (-not (Test-Path $pluginDir)) {
+    Write-Host "`n  Plugin directory NOT FOUND at $pluginDir" -ForegroundColor Red
+    Write-Host "  The plugin may not be installed, or Disco may use a different path." -ForegroundColor Yellow
+    Write-Host "  Try searching: Get-ChildItem 'C:\' -Recurse -Filter '$PluginName' -Directory -ErrorAction SilentlyContinue" -ForegroundColor Yellow
+    exit 1
+}
+
+Write-Host "`n--- Installed Files ---" -ForegroundColor Yellow
+Get-ChildItem $pluginDir -File | ForEach-Object {
+    $size = [math]::Round($_.Length / 1KB, 1)
+    Write-Host "  $($_.Name) ($size KB) - Modified: $($_.LastWriteTime.ToString('yyyy-MM-dd HH:mm:ss'))" -ForegroundColor Gray
+}
+
+# Check manifest
+$manifestPath = Join-Path $pluginDir "manifest.json"
+if (-not (Test-Path $manifestPath)) {
+    Write-Host "`n  [CRITICAL] manifest.json NOT FOUND in installed plugin directory!" -ForegroundColor Red
+    exit 1
+}
+
+Write-Host "`n--- Installed Manifest ---" -ForegroundColor Yellow
+$manifestContent = Get-Content $manifestPath -Raw
+$manifestObj = $manifestContent | ConvertFrom-Json
+
+Write-Host "  Id:       $($manifestObj.Id)" -ForegroundColor Gray
+Write-Host "  Version:  $($manifestObj.Version)" -ForegroundColor Gray
+Write-Host "  TypeName: $($manifestObj.TypeName)" -ForegroundColor Gray
+
+if (-not $manifestObj.Features -or $manifestObj.Features.Count -eq 0) {
+    Write-Host "`n  [ROOT CAUSE] Features array is EMPTY or MISSING!" -ForegroundColor Red
+    Write-Host "  This means Disco has no UIExtension features to load for this plugin." -ForegroundColor Red
+    Write-Host "  The plugin will initialize but UIExtensions will never render." -ForegroundColor Red
+    Write-Host "`n  FIX: Re-build with the updated Build-Plugin.ps1 and re-import the .discoPlugin file." -ForegroundColor Yellow
+    Write-Host "  The new build script generates the Features array in manifest.json." -ForegroundColor Yellow
+} else {
+    Write-Host "  Features: $($manifestObj.Features.Count) found" -ForegroundColor Green
+
+    $expectedCategory = 'Disco.Services.Plugins.Features.UIExtension.UIExtensionFeature`1'
+
+    foreach ($feature in $manifestObj.Features) {
+        Write-Host "`n  Feature: $($feature.Id)" -ForegroundColor Cyan
+        Write-Host "    TypeName:         $($feature.TypeName)" -ForegroundColor Gray
+        Write-Host "    CategoryTypeName: $($feature.CategoryTypeName)" -ForegroundColor Gray
+
+        if ($feature.CategoryTypeName -eq $expectedCategory) {
+            Write-Host "    CategoryTypeName: VALID" -ForegroundColor Green
+        } else {
+            Write-Host "    CategoryTypeName: MISMATCH (expected: $expectedCategory)" -ForegroundColor Red
+        }
+    }
+}
+
+# Check Disco logs for plugin initialization
+Write-Host "`n--- Disco Log Check ---" -ForegroundColor Yellow
+$logDir = Join-Path $DiscoPath "App_Data\Logs"
+if (Test-Path $logDir) {
+    $recentLog = Get-ChildItem $logDir -Filter "*.log" -ErrorAction SilentlyContinue |
+        Sort-Object LastWriteTime -Descending | Select-Object -First 1
+
+    if ($recentLog) {
+        Write-Host "  Most recent log: $($recentLog.Name) ($($recentLog.LastWriteTime))" -ForegroundColor Gray
+        $pluginLines = Select-String -Path $recentLog.FullName -Pattern "ADCompare|$PluginName" -ErrorAction SilentlyContinue
+        if ($pluginLines) {
+            Write-Host "  Plugin-related log entries:" -ForegroundColor Gray
+            $pluginLines | Select-Object -Last 20 | ForEach-Object {
+                $line = $_.Line.Trim()
+                if ($line -match 'error|exception|fail') {
+                    Write-Host "    $line" -ForegroundColor Red
+                } elseif ($line -match 'warn') {
+                    Write-Host "    $line" -ForegroundColor Yellow
+                } else {
+                    Write-Host "    $line" -ForegroundColor DarkGray
+                }
+            }
+        } else {
+            Write-Host "  No plugin-related entries found in latest log." -ForegroundColor Yellow
+        }
+    } else {
+        Write-Host "  No log files found in $logDir" -ForegroundColor Yellow
+    }
+} else {
+    Write-Host "  Log directory not found at $logDir" -ForegroundColor Yellow
+}
+
+# Dump raw manifest
+Write-Host "`n--- Raw Installed manifest.json ---" -ForegroundColor DarkGray
+$manifestContent -split "`n" | ForEach-Object {
+    Write-Host "  $_" -ForegroundColor DarkGray
+}
+Write-Host "--- End ---" -ForegroundColor DarkGray