Fix codecov coverage for Cython modules

[kfir4444]

No description provided.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 58.59%. Comparing base (ccb9f71) to head (a9a880a).
⚠️ Report is 2 commits behind head on main.

❗ There is a different number of reports uploaded between BASE (ccb9f71) and HEAD (a9a880a). Click for more details.

HEAD has 6 uploads less than BASE

Flag	BASE (ccb9f71)	HEAD (a9a880a)
unittests	4	1
functionaltests	4	1

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #837      +/-   ##
==========================================
- Coverage   67.44%   58.59%   -8.85%     
==========================================
  Files         156       97      -59     
  Lines       46319    29197   -17122     
  Branches     8506     7752     -754     
==========================================
- Hits        31241    17109   -14132     
+ Misses      13210     9887    -3323     
- Partials     1868     2201     +333     

Flag	Coverage Δ
functionaltests	58.59% <ø> (-8.85%)	⬇️
unittests	58.59% <ø> (-8.85%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 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.

[Copilot]

Pull request overview

This PR updates ARC’s build and CI coverage configuration so Codecov correctly reports coverage for Cython-compiled modules.

Changes:

• Enable Cython line tracing and trace macros during extension builds when ARC_COVERAGE=1.
• Update CI to build with coverage instrumentation, collect functional-test coverage, and upload via codecov/codecov-action@v5.
• Configure Coverage.py to use the Cython.Coverage plugin and omit arc/**/*_test.py files from measured source.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
setup.py	Adds ARC_COVERAGE-gated Cython linetrace directives and CYTHON_TRACE macros to extension builds.
.github/workflows/ci.yml	Sets coverage env vars, appends functional-test coverage output, and updates Codecov action + inputs.
.coveragerc	Enables Cython.Coverage plugin and omits arc/**/*_test.py from coverage measurement.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[alongd]

Thanks!