Preserve splat sigils during variable rename

[Copilot]

Rename Symbol was rewriting splatted variable references from @name to $name when renaming a variable, producing invalid refactoring output for splat invocations. This updates variable rename handling so splat references keep their @ sigil.

• Rename behavior

  • Update RenameService to emit @NewName for VariableExpressionAst nodes marked as splatted, while preserving existing $NewName behavior for normal variable references.

• Regression coverage

  • Add a focused refactoring fixture covering a hashtable assignment plus Start-Process @SplatProcessss.
  • Register the fixture in the shared variable rename test cases so the end-to-end rename output is verified.

• Result

  • Renaming a splat variable now updates both the assignment and the invocation correctly.

$SplatProcessss = @{
    FilePath = 'C:\Windows\system32\cmd.exe'
}

Start-Process @SplatProcessss

Renaming SplatProcessss to SplatProcess now yields:

$SplatProcess = @{
    FilePath = 'C:\Windows\system32\cmd.exe'
}

Start-Process @SplatProcess

[JustinGrote]

@andyleejordan small fix, should be an easy approve.

[Copilot]

Pull request overview

This PR fixes a refactoring bug in PowerShell Editor Services' Rename Symbol feature. Previously, renaming a variable rewrote splatted references (e.g. @SplatProcessss in Start-Process @SplatProcessss) using the $ sigil instead of @, producing invalid PowerShell. The fix selects the correct sigil based on whether the VariableExpressionAst is splatted, and adds regression coverage.

Changes:

• In RenameService.GetRenameVariableEdit, emit @NewName for splatted variable references and keep $NewName for normal references, using the existing VariableExpressionAst.Splatted flag.
• Add a before/after fixture pair (VariableSplattedReference.ps1 / VariableSplattedReferenceRenamed.ps1) exercising a hashtable assignment plus a Start-Process @... splat invocation.
• Register the new fixture in the shared variable rename test cases so it is verified end-to-end.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/PowerShellEditorServices/Services/TextDocument/RenameService.cs	Picks @ vs $ sigil based on var.Splatted, following the existing char + NewName concatenation pattern.
test/.../Refactoring/Variables/VariableSplattedReference.ps1	New input fixture containing a splat assignment and splat invocation.
test/.../Refactoring/Variables/VariableSplattedReferenceRenamed.ps1	Expected output fixture after renaming to Renamed, preserving the @ sigil on the invocation.
test/.../Refactoring/Variables/_RefactorVariableTestCases.cs	Registers the new fixture (Line 1, Column 1) so the rename round-trip is asserted.

The change is minimal, follows the existing conditional-sigil concatenation style already used for $ and -, and is correctly covered by the new fixtures (the harness renames $SplatProcessss to the default Renamed and compares against the Renamed.ps1 fixture). I found no correctness, naming, or coverage issues.