fix: use consistent clock for span durations

[chrispader]

Explanation of Change

This draft follow-up depends on #98144.

Native startup spans can receive an epoch-based start time from the native app-start module. The benchmark logger previously stored that epoch timestamp directly and later subtracted it from process-relative performance.now(), producing durations around -1.785e12ms.

This change converts Sentry's accepted start-time representation to epoch milliseconds once, translates it into the current process's monotonic clock domain, and then calculates elapsed time entirely with performance.now(). It also keeps the diagnostic log timestamp in epoch milliseconds via Date.now().

A regression test covers an epoch-based startup span and verifies that a 750ms elapsed interval is logged as 750ms.

Fixed Issues

$
PROPOSAL:

Tests

Physical-device verification after rebuilding the release app is still pending, so this PR remains a draft.

1. Add the startup span to the git-ignored root .env:

   EXPO_PUBLIC_BENCHMARK_SENTRY_SPANS=ManualAppStartup

2. Build and install the release HybridApp from Mobile-Expensify.
3. Run:

   nr benchmark-app-startup ios 20 30 --span ManualAppStartup --device "Developer's iPhone" --app-id com.expensify.expensifylite

4. Verify all 20 durations are positive, plausible millisecond values rather than values near -1.785e12ms.
5. Verify the summary table and generated CSV contain those same positive durations.
6. Run nr test --runInBand --watchman=false tests/unit/ActiveSpansBenchmarkTest.ts and verify the epoch-based duration regression test passes.

• Verify that no errors appear in the JS console

Offline tests

Offline testing was not performed. The change only corrects local elapsed-time calculation and does not change network behavior.

QA Steps

This opt-in tooling is not enabled in standard staging builds. QA can validate it using the local release-build steps in ### Tests.

• Verify that no errors appear in the JS console

PR Author Checklist

• I linked the correct issue in the ### Fixed Issues section above
• I wrote clear testing steps that cover the changes made in this PR
  • I added steps for local testing in the Tests section
  • I added steps for the expected offline behavior in the Offline steps section
  • I added steps for Staging and/or Production testing in the QA steps section
  • I added steps to cover failure scenarios (i.e. verify an input displays the correct error message if the entered data is not correct)
  • I turned off my network connection and tested it while offline to ensure it matches the expected behavior (i.e. verify the default avatar icon is displayed if app is offline)
  • I tested this PR with a High Traffic account against the staging or production API to ensure there are no regressions (e.g. long loading states that impact usability).
• I included screenshots or videos for tests on all platforms
• I ran the tests on all platforms & verified they passed on:
  • Android: Native
  • Android: mWeb Chrome
  • iOS: Native
  • iOS: mWeb Safari
  • MacOS: Chrome / Safari
• I verified there are no console errors (if there's a console error not related to the PR, report it or open an issue for it to be fixed)
• I followed proper code patterns (see Reviewing the code)
  • I verified that comments were added to code that is not self explanatory
  • I verified that any new or modified comments were clear, correct English, and explained "why" the code was doing something instead of only explaining "what" the code was doing.
  • I verified any copy / text that was added to the app is grammatically correct in English. It adheres to proper capitalization guidelines (note: only the first word of header/labels should be capitalized), and is either coming verbatim from figma or has been approved by marketing (in order to get marketing approval, ask the Bug Zero team member to add the Waiting for copy label to the issue)
• If a new code pattern is added I verified it was agreed to be used by multiple Expensify engineers
• I followed the guidelines as stated in the Review Guidelines
• I tested other components that can be impacted by my changes (i.e. if the PR modifies a shared library or component like Avatar, I verified the components using Avatar are working as expected)
• If a new CSS style is added I verified that:
  • A similar style doesn't already exist
  • The style can't be created with an existing StyleUtils function (i.e. StyleUtils.getBackgroundAndBorderStyle(theme.componentBG))
• If new assets were added or existing ones were modified, I verified that:
  • The assets are optimized and compressed (for SVG files, run npm run compress-svg)
  • The assets load correctly across all supported platforms.
• If the PR modifies code that runs when editing or sending messages, I tested and verified there is no unexpected behavior for all supported markdown - URLs, single line code, code blocks, quotes, headings, bold, strikethrough, and italic.
• If the PR modifies a generic component, I tested and verified that those changes do not break usages of that component in the rest of the App (i.e. if a shared library or component like Avatar is modified, I verified that Avatar is working as expected in all cases)
• If the PR modifies a component related to any of the existing Storybook stories, I tested and verified all stories for that component are still working as expected.
• If the PR modifies a component or page that can be accessed by a direct deeplink, I verified that the code functions as expected when the deeplink is used - from a logged in and logged out account.
• If the PR modifies the UI (e.g. new buttons, new UI components, changing the padding/spacing/sizing, moving components, etc) or modifies the form input styles:
  • I verified that all the inputs inside a form are aligned with each other.
  • I added Design label and/or tagged @Expensify/design so the design team can review the changes.
• I added unit tests for any new feature or bug fix in this PR to help automatically prevent regressions in this user flow.
• If the main branch was merged into this PR after a review, I tested again and verified the outcome was still expected according to the Test steps.

Screenshots/Videos

No screenshots or videos are included because this change only corrects developer benchmark timing and does not modify the app UI.

[github-actions]

⚠️ This PR is possibly changing native code and/or updating libraries, it may cause problems with HybridApp. Please check if any patch updates are required in the HybridApp repo and run an AdHoc build to verify that HybridApp will not break. Ask Contributor Plus for help if you are not sure how to handle this. ⚠️

[codecov]

Codecov Report

✅ Changes either increased or maintained existing code coverage, great job!

Files with missing lines	Coverage Δ
src/libs/telemetry/activeSpans.ts	98.27% <100.00%> (+4.04%)	⬆️
src/libs/telemetry/logBenchmarkSpanEnd.ts	88.88% <88.88%> (ø)
src/libs/telemetry/writeBenchmarkLog/index.ios.ts	77.77% <77.77%> (ø)
src/libs/telemetry/writeBenchmarkLog/index.ts	0.00% <0.00%> (ø)
... and 277 files with indirect coverage changes

[chrispader]

Closing as a duplicate of #98152, which already contains the same clock-domain correction and regression coverage.