test coverage, profiling tests, and rearranging uv lock

[evinism]

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[Copilot]

Pull Request Overview

This PR enhances the test infrastructure by adding code coverage reporting and improving profiling output in tests. The changes configure pytest with coverage reporting and update the profiling test to output more useful statistics while saving profile data for analysis.

• Adds pytest-cov dependency and enables coverage reporting in CI
• Updates profiling test to output top 20 functions and save profile stats
• Migrates from optional-dependencies to dependency-groups in pyproject.toml

Reviewed Changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 1 comment.

File	Description
py/tests/test_performance.py	Improves profiling output by removing string buffer and showing top 20 stats
py/pyproject.toml	Adds pytest-cov dependency and migrates to dependency-groups format
.github/workflows/python.yml	Enables pytest coverage reporting and adds PROFILE environment variable

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[Copilot]

The installation command still references the old [dev] optional dependency format, but pyproject.toml has been updated to use dependency-groups. This should be changed to uv pip install -e . --group dev to match the new dependency-groups format.

Suggested change

	run: uv pip install -e ".[dev]"
	run: uv pip install -e . --group dev