Fix unhandled exception when evaluating sqrt(-1) in PowerToys Run Calculator

[Copilot]

sqrt(-1) caused an unhandled InvalidCastException in the Calculator plugin because the Mages engine returns System.Numerics.Complex for imaginary results, and Convert.ToDecimal() doesn't support it.

Summary of the Pull Request

Added a Complex type guard in TransformResult() so imaginary results surface as a user-friendly error instead of crashing.

// CalculateEngine.cs — TransformResult()
if (result is Complex)
{
    return Properties.Resources.wox_plugin_calculator_complex_number_result; // "Result is a complex number"
}

PR Checklist

• Closes: #xxx
• Communication: I've discussed this with core contributors already. If the work hasn't been agreed, this work might be rejected
• Tests: Added/updated and all pass
• Localization: All end-user-facing strings can be localized
• Dev docs: Added/updated
• New binaries: Added on the required places
  • JSON for signing for new binaries
  • WXS for installer for new binaries and localization folder
  • YML for CI pipeline for new test projects
  • YML for signed pipeline
• Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

Detailed Description of the Pull Request / Additional comments

• CalculateEngine.cs — Added using System.Numerics; and a Complex check in TransformResult() before the Convert.ToDecimal() call that was throwing.
• Resources.resx / Resources.Designer.cs — New resource string wox_plugin_calculator_complex_number_result = "Result is a complex number".

The existing pattern for unrepresentable results (NaN, Function, double[,]) already returns an error string from TransformResult(); this fix follows the same convention.

Validation Steps Performed

• Added [DataRow("=sqrt(-1)", "Result is a complex number")] to QueryTests.ErrorResultOnInvalidKeywordQuery.
• Added [DataRow("sqrt(-1)")] to ExtendedCalculatorParserTests.Interpret_NoResult_WhenCalled to confirm the engine returns default with a populated error string rather than throwing.

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[Copilot]

Pull request overview

Prevents a crash in the PowerToys Run Calculator plugin when the Mages engine evaluates expressions that yield an imaginary/complex result (e.g., sqrt(-1)), by converting that case into a localized, user-facing error.

Changes:

• Added a System.Numerics.Complex guard in CalculateEngine.TransformResult() to return an error string instead of reaching Convert.ToDecimal(...).
• Introduced a new localized resource string for complex-number results.
• Added unit test coverage to verify the user-visible error behavior for =sqrt(-1) and that the engine path no longer throws.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/modules/launcher/Plugins/Microsoft.PowerToys.Run.Plugin.Calculator/Properties/Resources.resx	Adds new localized string for complex-number results.
src/modules/launcher/Plugins/Microsoft.PowerToys.Run.Plugin.Calculator/Properties/Resources.Designer.cs	Exposes the new resource string via the strongly-typed resource accessor.
src/modules/launcher/Plugins/Microsoft.PowerToys.Run.Plugin.Calculator/CalculateEngine.cs	Guards complex results in TransformResult() to avoid invalid decimal conversion.
src/modules/launcher/Plugins/Microsoft.PowerToys.Run.Plugin.Calculator.UnitTest/QueryTests.cs	Verifies =sqrt(-1) produces the expected user-facing error.
src/modules/launcher/Plugins/Microsoft.PowerToys.Run.Plugin.Calculator.UnitTest/ExtendedCalculatorParserTests.cs	Ensures sqrt(-1) yields no result (no exception) in engine-level parsing.

Files not reviewed (1)

• src/modules/launcher/Plugins/Microsoft.PowerToys.Run.Plugin.Calculator/Properties/Resources.Designer.cs: Language not supported

[MuyuanMS]

Seems to be duplicated with work #47506