coverage-diff-reporter

Overview

A whole-repo coverage gate is necessary but not sufficient. A drop of 0.4pp overall might hide a 12pp drop in one critical file. A new file at 35% line coverage might pass an aggregate gate but leave a regression-risk hot spot.

This skill builds a coverage diff report that solves the "reviewer can see what to look at" problem:

1. Parse the current run's coverage (LCOV / Cobertura).
2. Parse a baseline from the merge target.
3. Emit a per-file delta table sorted by absolute drop.
4. Highlight new files below threshold, files with disproportionate drops, and files that gained coverage (positive feedback).
5. Post a single-line summary as the PR top-of-comment, with click-through to the full table.