ci: enable Codecov Test Analytics across all test jobs

[Yicong-Huang]

What changes were proposed in this PR?

Enable Codecov Test Analytics for every stack we already upload coverage from. Each stack now emits JUnit-XML alongside its existing coverage report, and a second codecov/codecov-action step per job uploads it with report_type: test_results.

• ScalaTest: ThisBuild / Test / testOptions += -u target/test-reports in the root build.sbt.
• Vitest unit + browser configs: reporters: ["default", ["junit", { outputFile: ... }]].
• pytest (python job + amber-integration Python step): --junit-xml=....
• bun test (agent-service): --reporter=junit --reporter-outfile=junit.xml.

Test Analytics ingestion is independent of coverage and shares the same CODECOV_TOKEN. Once landed, Codecov will start posting failing-test stack traces on PRs, flagging tests that have gone flaky on main, and tracking per-test runtime / failure-rate over time.

Any related issues, documentation, discussions?

Closes #5206.

How was this PR tested?

Ran sbt scalafmtCheckAll and prettier --check on the two modified vitest.*.config.ts files locally; both pass.

Was this PR authored or co-authored using generative AI tooling?

Generated-by: Claude Opus 4.7

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 47.13%. Comparing base (c435aa7) to head (75048c2).

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #5207      +/-   ##
============================================
- Coverage     47.15%   47.13%   -0.03%     
+ Complexity     2348     2343       -5     
============================================
  Files          1042     1042              
  Lines         39989    39989              
  Branches       4260     4260              
============================================
- Hits          18855    18847       -8     
- Misses        20012    20015       +3     
- Partials       1122     1127       +5     

Flag	Coverage Δ
access-control-service	39.53% <ø> (ø)
agent-service	33.76% <ø> (ø)
amber	50.31% <ø> (-0.06%)	⬇️
computing-unit-managing-service	0.00% <ø> (ø)
config-service	0.00% <ø> (ø)
file-service	32.18% <ø> (ø)
frontend	37.81% <ø> (ø)
python	90.50% <ø> (ø)
workflow-compiling-service	56.81% <ø> (ø)

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