fix: use document line endings in code fix providers for cross-platform CI

Code fix providers for BWFC002, BWFC004, BWFC010, BWFC012 hardcoded \r\n
in EndOfLine trivia, causing test failures on Linux CI runners where
source files have \n line endings.

Added SyntaxExtensions.DetectEndOfLine() helper that reads the first
EndOfLineTrivia from the syntax tree, ensuring code fixes match the
document's existing line ending style.

Fixes failing tests in PR FritzAndFriends#487.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: csharpfritz

src/BlazorWebFormsComponents.Analyzers/EventHandlerSignatureCodeFixProvider.cs

@@ -58,7 +58,7 @@ private async Task<Document> AddTodoCommentAsync(Document document, MethodDeclar
 
             var newLeadingTrivia = method.GetLeadingTrivia()
                 .Add(todoComment)
-                .Add(SyntaxFactory.EndOfLine("\r\n"));
+                .Add(root.DetectEndOfLine());
 
             // Collect indentation from original method
             foreach (var trivia in method.GetLeadingTrivia())

src/BlazorWebFormsComponents.Analyzers/RequiredAttributeCodeFixProvider.cs

@@ -57,7 +57,7 @@ private async Task<Document> AddTodoCommentAsync(Document document, SyntaxNode n
 
             var newLeadingTrivia = statement.GetLeadingTrivia()
                 .Insert(0, todoComment)
-                .Insert(1, SyntaxFactory.EndOfLine("\r\n"));
+                .Insert(1, root.DetectEndOfLine());
 
             var newStatement = statement.WithLeadingTrivia(newLeadingTrivia);
             var newRoot = root.ReplaceNode(statement, newStatement);

src/BlazorWebFormsComponents.Analyzers/ResponseRedirectCodeFixProvider.cs

@@ -64,7 +64,7 @@ private async Task<Document> ReplaceWithTodoCommentAsync(Document document, Synt
             // Build leading trivia: original leading + comment + newline + indentation for the ;
             var leading = statement.GetLeadingTrivia()
                 .Add(todoComment)
-                .Add(SyntaxFactory.EndOfLine("\r\n"))
+                .Add(root.DetectEndOfLine())
                 .AddRange(indentation);
 
             var emptyStatement = SyntaxFactory.EmptyStatement()

src/BlazorWebFormsComponents.Analyzers/SessionUsageCodeFixProvider.cs

@@ -64,7 +64,7 @@ private async Task<Document> ReplaceWithTodoCommentAsync(Document document, Synt
             // Build leading trivia: original leading + comment + newline + indentation for the ;
             var leading = statement.GetLeadingTrivia()
                 .Add(todoComment)
-                .Add(SyntaxFactory.EndOfLine("\r\n"))
+                .Add(root.DetectEndOfLine())
                 .AddRange(indentation);
 
             var emptyStatement = SyntaxFactory.EmptyStatement()

src/BlazorWebFormsComponents.Analyzers/SyntaxExtensions.cs

@@ -0,0 +1,25 @@
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+
+namespace BlazorWebFormsComponents.Analyzers
+{
+    internal static class SyntaxExtensions
+    {
+        /// <summary>
+        /// Detects the line ending style used in the syntax tree and returns a matching
+        /// EndOfLine trivia. Falls back to <c>\n</c> if no existing line endings are found.
+        /// </summary>
+        internal static SyntaxTrivia DetectEndOfLine(this SyntaxNode root)
+        {
+            foreach (var trivia in root.DescendantTrivia())
+            {
+                if (trivia.IsKind(SyntaxKind.EndOfLineTrivia))
+                {
+                    return trivia;
+                }
+            }
+
+            return SyntaxFactory.EndOfLine("\n");
+        }
+    }
+}