fix(solid/tanstackrouter): Ensure web vitals are sent on pageload

[logaretm]

Adjusted the condition for reporting web vitals previously it would short circuit and prevent them from being reported, I included a test.

similar to what we did in #18463

closes #18540

[linear]

JS-1323 [Solid] Core Web Vitals aren't reported with Tanstack Router integration

[Copilot]

Pull request overview

This PR fixes an issue where web vitals were not being sent on pageload in the Solid TanStack Router integration. The problem was caused by a conditional check that would short-circuit during initial pageload, preventing the pageload transaction from completing and sending web vitals measurements.

• Updated the navigation span filtering logic to explicitly check for absence of fromLocation before comparing location states
• Added comprehensive test coverage to verify web vitals are sent on pageload

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
packages/solid/src/tanstackrouter.ts	Fixed the condition in onBeforeNavigate callback to properly detect initial pageload by checking for absence of fromLocation before comparing location states
dev-packages/e2e-tests/test-applications/solid-tanstack-router/tests/routing-instrumentation.test.ts	Added test case to verify pageload transactions include web vitals measurements (ttfb, lcp, fp, fcp)

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[andreiborza]

Thanks for taking care of this 🙏

[Lms24]

Thanks!