refactor: Use XML parsing instead of string parsing for project dependencies (#1645) (#1713)

* refactor: Use XML parsing instead of string parsing for project dependencies

Replace fragile string parsing with proper XML parsing using XDocument
to extract ProjectReference elements from .csproj files.

Benefits:
- More robust and reliable parsing
- Handles all formatting variations correctly
- Platform-independent path handling with Path.GetFileName
- Follows the same pattern used elsewhere in the codebase

Fixes #1645

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix: Dispose FileStream properly and use OfType<string>

- Fix resource leak by wrapping FileStream in await using statement
- Use .OfType<string>() instead of .Where(v => v != null) for better
  null handling and type safety

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* refactor: Use ProjectRootElement instead of XDocument for consistency

Replace XDocument-based XML parsing with ProjectRootElement from
Microsoft.Build.Construction, matching the existing pattern used in
GenerateReadMeModule.cs. This provides a more idiomatic approach for
parsing MSBuild project files.

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: thomhurst

src/ModularPipelines.Build/Modules/FindProjectDependenciesModule.cs

@@ -1,3 +1,4 @@
+using Microsoft.Build.Construction;
 using Microsoft.Extensions.Logging;
 using ModularPipelines.Attributes;
 using ModularPipelines.Context;
@@ -9,23 +10,23 @@ namespace ModularPipelines.Build.Modules;
 [DependsOn<FindProjectsModule>]
 public class FindProjectDependenciesModule : Module<FindProjectDependenciesModule.ProjectDependencies>
 {
-    public override async Task<ProjectDependencies?> ExecuteAsync(IModuleContext context, CancellationToken cancellationToken)
+    public override Task<ProjectDependencies?> ExecuteAsync(IModuleContext context, CancellationToken cancellationToken)
     {
         var projects = context.GetModule<FindProjectsModule, IReadOnlyList<File>>();
 
         var dependencies = new List<File>();
 
         foreach (var file in projects.Value!)
         {
-            await foreach (var line in file.ReadLinesAsync(cancellationToken))
-            {
-                if (!line.Contains("<ProjectReference"))
-                {
-                    continue;
-                }
+            var projectRootElement = ProjectRootElement.Open(file)!;
 
-                var name = line.Split('\\').Last().Split('"').First();
+            var projectReferences = projectRootElement.Items
+                .Where(i => i.ItemType == "ProjectReference")
+                .Select(i => i.Include);
 
+            foreach (var reference in projectReferences)
+            {
+                var name = Path.GetFileName(reference);
                 var project = projects.Value!.FirstOrDefault(x => x.Name == name);
 
                 if (project != null)
@@ -39,7 +40,7 @@ public class FindProjectDependenciesModule : Module<FindProjectDependenciesModul
 
         LogProjects(context, projectDependencies);
 
-        return projectDependencies;
+        return Task.FromResult<ProjectDependencies?>(projectDependencies);
     }
 
     private static void LogProjects(IModuleContext context, ProjectDependencies projectDependencies)