refactor(sitemap): simplify ExtractIndexableRoutes to derive from static routes

Address PR feedback:
- Remove IsApiController() and ContainsRouteParameters() helpers — eliminates
  code duplication between ExtractStaticRoutes and ExtractIndexableRoutes
- Derive indexable routes from _StaticRoutes via LINQ filters, so the two
  sets can never diverge unintentionally
- Add Identity route exclusion (was lost when inline filter was removed)
- Cache route-parameter regex as static readonly to avoid repeated Regex
  construction on each call (no more Regex.IsMatch with a pattern literal)
- Remove 'using Microsoft.AspNetCore.Mvc.Abstractions' — no longer needed

Author: BenjaminMichaelis

EssentialCSharp.Web/Services/RouteConfigurationService.cs

@@ -1,12 +1,13 @@
-using Microsoft.AspNetCore.Mvc;
-using Microsoft.AspNetCore.Mvc.Abstractions;
 using Microsoft.AspNetCore.Mvc.Infrastructure;
 using System.Text.RegularExpressions;
 
 namespace EssentialCSharp.Web.Services;
 
 public class RouteConfigurationService : IRouteConfigurationService
 {
+    private static readonly Regex s_routeParameterRegex =
+        new(@"\{[^}]+\}|\[[^\]]+\]", RegexOptions.Compiled);
+
     private readonly IActionDescriptorCollectionProvider _ActionDescriptorCollectionProvider;
     private readonly HashSet<string> _StaticRoutes;
     private readonly HashSet<string> _IndexableRoutes;
@@ -72,80 +73,11 @@ private HashSet<string> ExtractStaticRoutes()
 
     private HashSet<string> ExtractIndexableRoutes()
     {
-        var indexableRoutes = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
-        
-        // Get all action descriptors
-        var actionDescriptors = _ActionDescriptorCollectionProvider.ActionDescriptors.Items;
-        
-        foreach (var actionDescriptor in actionDescriptors)
-        {
-            // Skip if controller is marked with [ApiController]
-            if (IsApiController(actionDescriptor))
-                continue;
-
-            // Look for route attributes
-            if (actionDescriptor.AttributeRouteInfo?.Template != null)
-            {
-                string template = actionDescriptor.AttributeRouteInfo.Template;
-                
-                // Skip routes with parameters (e.g., {chapter}, {id:guid}, [optional])
-                if (ContainsRouteParameters(template))
-                    continue;
-                
-                // Skip routes starting with /api/
-                if (template.StartsWith("/api/", StringComparison.OrdinalIgnoreCase))
-                    continue;
-                
-                // Remove leading slash and add to our set
-                string routePath = template.TrimStart('/').ToLowerInvariant();
-                indexableRoutes.Add(routePath);
-            }
-
-            // Skip the default fallback route (Index action in HomeController)
-            if (actionDescriptor.RouteValues.TryGetValue("action", out var action) && action == "Index")
-                continue;
-
-            // Skip Error actions
-            if (action == "Error")
-                continue;
-
-            // For actions without attribute routes, use conventional routing
-            if (actionDescriptor.AttributeRouteInfo?.Template == null &&
-                actionDescriptor.RouteValues.TryGetValue("action", out var actionName) &&
-                actionDescriptor.RouteValues.TryGetValue("controller", out var controllerName) &&
-                controllerName?.Equals("Home", StringComparison.OrdinalIgnoreCase) == true &&
-                actionName != null)
-            {
-                // Use the action name directly as the route
-                indexableRoutes.Add(actionName.ToLowerInvariant());
-            }
-        }
-
-        return indexableRoutes;
-    }
-
-    private static bool IsApiController(ActionDescriptor actionDescriptor)
-    {
-        // Check for [ApiController] attribute
-        if (actionDescriptor.EndpointMetadata?.OfType<ApiControllerAttribute>().Any() == true)
-            return true;
-        
-        // Check if controller inherits from ControllerBase (not Controller)
-        if (actionDescriptor.RouteValues.TryGetValue("controller", out var controllerName))
-        {
-            // Known API controllers
-            var apiControllers = new[] { "ListingSourceCode", "Chat", "McpToken", "MCP" };
-            if (apiControllers.Contains(controllerName, StringComparer.OrdinalIgnoreCase))
-                return true;
-        }
-        
-        return false;
-    }
-
-    private static bool ContainsRouteParameters(string template)
-    {
-        // Match {param}, {param:constraint}, [optional], etc.
-        return Regex.IsMatch(template, @"\{[^}]+\}|\[[^\]]+\]");
+        return _StaticRoutes
+            .Where(route => !route.StartsWith("api/", StringComparison.OrdinalIgnoreCase))
+            .Where(route => !s_routeParameterRegex.IsMatch(route))
+            .Where(route => !route.Contains("identity", StringComparison.OrdinalIgnoreCase))
+            .ToHashSet(StringComparer.OrdinalIgnoreCase);
     }
 }