Add parser test for attributes after Razor comments

Added test to verify the HTML parser correctly handles attributes after Razor comments.

Co-authored-by: davidwengier <754264+davidwengier@users.noreply.github.com>

Author: Copilot

src/Compiler/Microsoft.AspNetCore.Razor.Language/test/Legacy/HtmlAttributeTest.cs

@@ -344,6 +344,12 @@ public void ConditionalAttribute_CommentBefore()
         ParseDocumentTest("""<p @* comment *@ class="@c" />""");
     }
 
+    [Fact, WorkItem("https://github.com/dotnet/razor/issues/12261")]
+    public void AttributeAfterComment()
+    {
+        ParseDocumentTest("""<p class="first" @* comment *@ data-value="second" />""");
+    }
+
     [Fact]
     public void EscapedAttributeName_WithValue()
     {

src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/ParserTests/HtmlAttributeTest/AttributeAfterComment.cspans.txt

@@ -0,0 +1,14 @@
+Markup span at (0:0,0 [2] ) - Parent: Tag block at (0:0,0 [53] )
+Markup span at (2:0,2 [8] ) - Parent: Markup block at (2:0,2 [14] )
+Markup span at (10:0,10 [5] ) - Parent: Markup block at (2:0,2 [14] )
+Markup span at (15:0,15 [1] ) - Parent: Markup block at (2:0,2 [14] )
+Markup span at (16:0,16 [1] ) - Parent: Tag block at (0:0,0 [53] )
+Transition span at (17:0,17 [1] ) - Parent: Comment block at (17:0,17 [13] )
+MetaCode span at (18:0,18 [1] ) - Parent: Comment block at (17:0,17 [13] )
+Comment span at (19:0,19 [9] ) - Parent: Comment block at (17:0,17 [13] )
+MetaCode span at (28:0,28 [1] ) - Parent: Comment block at (17:0,17 [13] )
+Transition span at (29:0,29 [1] ) - Parent: Comment block at (17:0,17 [13] )
+Markup span at (30:0,30 [13] ) - Parent: Markup block at (30:0,30 [20] )
+Markup span at (43:0,43 [6] ) - Parent: Markup block at (30:0,30 [20] )
+Markup span at (49:0,49 [1] ) - Parent: Markup block at (30:0,30 [20] )
+Markup span at (50:0,50 [3] ) - Parent: Tag block at (0:0,0 [53] )

src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/ParserTests/HtmlAttributeTest/AttributeAfterComment.stree.txt

@@ -0,0 +1,47 @@
+RazorDocument - [0..53)::53 - [<p class="first" @* comment *@ data-value="second" />]
+    MarkupBlock - [0..53)::53
+        MarkupElement - [0..53)::53
+            MarkupStartTag - [0..53)::53 - [<p class="first" @* comment *@ data-value="second" />] - Gen<Markup>
+                OpenAngle;[<];
+                Text;[p];
+                MarkupAttributeBlock - [2..16)::14 - [ class="first"]
+                    MarkupTextLiteral - [2..3)::1 - [ ] - Gen<Markup>
+                        Whitespace;[ ];
+                    MarkupTextLiteral - [3..8)::5 - [class] - Gen<Markup>
+                        Text;[class];
+                    Equals;[=];
+                    MarkupTextLiteral - [9..10)::1 - ["] - Gen<Markup>
+                        DoubleQuote;["];
+                    GenericBlock - [10..15)::5
+                        MarkupLiteralAttributeValue - [10..15)::5 - [first]
+                            MarkupTextLiteral - [10..15)::5 - [first] - Gen<Markup>
+                                Text;[first];
+                    MarkupTextLiteral - [15..16)::1 - ["] - Gen<Markup>
+                        DoubleQuote;["];
+                MarkupTextLiteral - [16..17)::1 - [ ] - Gen<Markup>
+                    Whitespace;[ ];
+                RazorComment - [17..30)::13
+                    RazorCommentTransition;[@];
+                    RazorCommentStar;[*];
+                    RazorCommentLiteral;[ comment ];
+                    RazorCommentStar;[*];
+                    RazorCommentTransition;[@];
+                MarkupAttributeBlock - [30..50)::20 - [ data-value="second"]
+                    MarkupTextLiteral - [30..31)::1 - [ ] - Gen<Markup>
+                        Whitespace;[ ];
+                    MarkupTextLiteral - [31..41)::10 - [data-value] - Gen<Markup>
+                        Text;[data-value];
+                    Equals;[=];
+                    MarkupTextLiteral - [42..43)::1 - ["] - Gen<Markup>
+                        DoubleQuote;["];
+                    GenericBlock - [43..49)::6
+                        MarkupTextLiteral - [43..49)::6 - [second] - Gen<Markup>
+                            Text;[second];
+                    MarkupTextLiteral - [49..50)::1 - ["] - Gen<Markup>
+                        DoubleQuote;["];
+                MarkupMiscAttributeContent - [50..51)::1
+                    MarkupTextLiteral - [50..51)::1 - [ ] - Gen<Markup>
+                        Whitespace;[ ];
+                ForwardSlash;[/];
+                CloseAngle;[>];
+    EndOfFile;[];