build(deps): update NuGet packages

[glennawatson]

Summary

Update the NuGet dependencies.

• Use ReactiveUI 26.0.1.
• Use Binding 9.1.0 and Primitives 9.0.0.
• Update TUnit to 1.72.16.
• Collect coverage when CI maps source paths.

Why

Pick up the XAML binding generator performance fix.

Breaking changes

Requires ReactiveUI 26.0.1.

How this was verified

Built the solution. Ran the desktop test suite. CI covers the platform builds.

Notes for the reviewer

The collector must include assemblies whose source paths are mapped by CI.

Checklist

• I have read the Contribute guide
• The PR title follows Conventional Commits
• Tests cover this change, or the summary says why they do not
• New or changed public API has XML documentation

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (c30a73e) to head (7c439ea).
⚠️ Report is 72 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##             main      #440       +/-   ##
============================================
+ Coverage   26.36%   100.00%   +73.63%     
============================================
  Files          16         5       -11     
  Lines        1134       122     -1012     
  Branches      171         9      -162     
============================================
- Hits          299       122      -177     
+ Misses        826         0      -826     
+ Partials        9         0        -9     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.