fix: trim rock paper scissors input

[vycdev2]

Summary

• Trim surrounding whitespace before the existing invariant case normalization for Rock Paper Scissors choices.
• Extend the existing regression coverage with padded mixed-case input.

Verification

• dotnet restore Morpheus.sln — passed (existing NU1903 warning).
• dotnet build Morpheus.sln --no-restore — passed with 0 errors.
• dotnet test Morpheus.Tests/Morpheus.Tests.csproj --no-build --filter FullyQualifiedName~NormalizeRockPaperScissorsChoice — passed (3/3).
• dotnet test Morpheus.sln --no-build — 297 passed; 2 unchanged tr-TR tests failed because this runner uses globalization-invariant mode.
• git diff --check — passed.

Risk

• Low: valid choices retain existing behavior; only surrounding whitespace is newly accepted.

This was generated by an AI agent (vycdev2). Please verify any changes before merging or applying.