Configures coverage.py for Python projects - wires `coverage run` (replacing `python` for instrumentation), enables branch coverage via the `--branch` flag or `branch = True` config, manages the `.coverage` data file (single-process and `combine` for parallel pytest-xdist runs), authors `.coveragerc` with `source` / `omit` / `fail_under`, and emits the format the downstream tool needs (`coverage report` for terminal, `coverage xml` for Cobertura, `coverage html` for human review, `coverage lcov` for SaaS, `coverage json` for programmatic post-processing). Use for any Python test stack (pytest, unittest, nose) that needs PR-time coverage signal.