refactor: move pytest-cov to lint dependency group

[lemenkov]

What I did

Move pytest-cov from default test options to optional lint group to make it easier for downstream users and packagers to run functional tests without requiring code quality/coverage tools.

fixes: #

How I did it

• Removed coverage-related flags from [tool.pytest.ini_options] addopts
• Moved pytest-cov from the test dependency group to the lint group
• Updated .github/workflows/test.yaml to explicitly pass coverage flags when needed:
  • Added --group lint to the functional test job
  • Added explicit coverage flags: --cov --cov-branch --cov-report=term --cov-report=xml --cov=eip712
  • Removed --no-cov from fuzzing job (no longer needed)

How to verify it

Default pytest run (no coverage):

uv run --group test pytest

This should run tests without attempting to collect coverage.

With coverage (for CI/development):

uv run --group test --group lint pytest --cov=eip712 --cov-branch --cov-report=term

This should work as before, collecting coverage reports.

GitHub Actions:
All existing CI workflows should continue to work unchanged, still collecting coverage as configured.

Why this change?

Currently, pytest-cov runs automatically on every pytest invocation, which creates issues:

1. Unnecessary dependency: Coverage is a development/CI tool, not required for validating functionality. Users running tests to verify correct installation shouldn't need pytest-cov installed.

2. Compatibility concerns: Coverage tools can be slow to adapt to new Python versions, potentially blocking early testing with Python alpha/beta releases.

3. Build system conflicts: Some distribution build systems (like Fedora's RPM packaging) have policies against running code quality tools during package builds, preferring to focus purely on functional testing.

4. Clearer dependency separation: This aligns with the existing structure where code quality tools (ruff, mypy) are in the lint group, separate from functional test requirements.

Benefits

• pytest now runs minimal, fast tests by default
• Developers can still collect coverage by passing flags or installing lint group
• CI/CD workflows remain unchanged (coverage still collected)
• Easier for downstream packagers and users to run functional tests
• Better separation: test dependencies vs. development/quality dependencies

Checklist

• All changes are completed
• New test cases have been added (N/A - infrastructure change)
• Documentation has been updated (N/A - workflow change only)

[fubuloubu]

You can run it without coverage via pytest --no-cov

Not sure I share your concern, at the very least I wouldn't put it under linting tools