fix: preserve splat sigil during rename

Author: Copilot

src/PowerShellEditorServices/Services/TextDocument/RenameService.cs

@@ -472,7 +472,7 @@ private TextEdit GetRenameVariableEdit(Ast ast)
                 ? throw new HandlerErrorException($"${NewName} is not a valid variable name.")
                 : new TextEdit
                 {
-                    NewText = '$' + NewName,
+                    NewText = (var.Splatted ? '@' : '$') + NewName,
                     Range = new ScriptExtentAdapter(var.Extent)
                 },
             StringConstantExpressionAst stringAst => !IsValidVariableName(NewName)

test/PowerShellEditorServices.Test.Shared/Refactoring/Variables/VariableSplattedReference.ps1

@@ -0,0 +1,5 @@
+$SplatProcessss = @{
+    FilePath = 'C:\Windows\system32\cmd.exe'
+}
+
+Start-Process @SplatProcessss

test/PowerShellEditorServices.Test.Shared/Refactoring/Variables/VariableSplattedReferenceRenamed.ps1

@@ -0,0 +1,5 @@
+$Renamed = @{
+    FilePath = 'C:\Windows\system32\cmd.exe'
+}
+
+Start-Process @Renamed

test/PowerShellEditorServices.Test.Shared/Refactoring/Variables/_RefactorVariableTestCases.cs

@@ -32,6 +32,7 @@ public static class RefactorVariableTestCases
         new ("VariableRedefinition.ps1",                       Line:  1, Column:  1),
         new ("VariableScriptWithParamBlock.ps1",               Line:  1, Column: 30),
         new ("VariableSimpleFunctionParameter.ps1",            Line:  6, Column:  9),
+        new ("VariableSplattedReference.ps1",                  Line:  1, Column:  1),
         new ("VariableusedInWhileLoop.ps1",                    Line:  2, Column:  5),
         new ("VariableWithinCommandAstScriptBlock.ps1",        Line:  3, Column: 75),
         new ("VariableWithinForeachObject.ps1",                Line:  2, Column:  1),