fix(blazor): Skip duplicate navigation breadcrumbs in WASM

[bruno-garcia]

Summary

• Fixes duplicate navigation breadcrumbs in Blazor WASM apps where LocationChanged fires twice for the same URL (e.g. when links use both @onclick+NavigateTo() and href)
• The fix is in the SDK (BlazorWasmOptionsSetup), not the sample app — customers shouldn't need to change their apps
• Skips creating a breadcrumb when args.Location matches previousUrl

Test plan

• New unit test: DuplicateNavigation_SkipsBreadcrumb
• All 9 unit tests pass (net8.0, net9.0, net10.0)
• Verified with sample app in browser — navigation creates exactly 1 breadcrumb per click (was 2 before fix)

🤖 Generated with Claude Code

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#skip-changelog
justification: #4907 has not been released yet

[github-actions]

Semver Impact of This PR

⚪ None (no version bump detected)

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[Copilot]

Pull request overview

This PR updates the Blazor WebAssembly sample app’s navigation menu to avoid generating duplicate LocationChanged-driven navigation breadcrumbs when users click links, aligning behavior with the breadcrumb tracking added in #4907.

Changes:

• Adds @onclick:preventDefault to menu links that also have @onclick handlers and href attributes.
• Prevents the anchor’s default navigation so only the explicit NavigateTo() call drives route changes.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.87%. Comparing base (14ec84f) to head (8ab742f).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4922   +/-   ##
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  Coverage   73.86%   73.87%           
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  Files         496      496           
  Lines       17921    17927    +6     
  Branches     3510     3511    +1     
=======================================
+ Hits        13237    13243    +6     
  Misses       3824     3824           
  Partials      860      860           

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