Fix TheoryDataRow traits not discovered in UI theory discoverers

[Copilot]

Traits set via TheoryDataRow.WithTrait() were silently dropped during test discovery for WpfTheory, StaTheory, UITheory, and WinFormsTheory, causing --filter-trait to return zero tests.

Root cause

Utilities.CreateTestCaseForDataRow called a private GetTraits(testMethod) that only read testMethod.Traits, ignoring traits on the ITheoryDataRow itself.

Fix

• Sdk/Utilities.cs: Replace GetTraits(testMethod) with TestIntrospectionHelper.GetTraits(testMethod, dataRow) in CreateTestCaseForDataRow — the xunit-provided overload that merges method-level and data-row-level traits.

Tests

Added TheoryDataRowTraitsAreDiscovered to each affected theory test class using:

public static IEnumerable<TheoryDataRow<string>> TraitDataRows =>
[
    new TheoryDataRow<string>("hello")
        .WithTrait("rowid", "properties"),
];

[UITheory]
[MemberData(nameof(TraitDataRows))]
public void TheoryDataRowTraitsAreDiscovered(string s) { ... }

Running -- --filter-trait "rowid=properties" now correctly discovers and runs these tests.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.55%. Comparing base (64640e4) to head (c590e2a).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #183   +/-   ##
=======================================
  Coverage   83.55%   83.55%           
=======================================
  Files          36       36           
  Lines         742      742           
  Branches       64       64           
=======================================
  Hits          620      620           
  Misses        100      100           
  Partials       22       22           

Flag	Coverage Δ
Linux	80.43% <100.00%> (ø)
Windows	79.11% <100.00%> (ø)
macOS	80.43% <100.00%> (ø)

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