feat(coverage): add cj/--coverage-parse-lcov helper

First of three pure helpers for the coverage-report command. Reads an LCOV file and returns a hash table of file to set of covered line numbers. Only the SF, DA, and end_of_record fields are interpreted. Other LCOV fields (FN, FNDA, LF, LH, BRDA) are ignored. Malformed DA lines are skipped silently so partial runs still yield usable data.

Tests cover Normal (single file, multiple files, mixed hit counts), Boundary (empty file, spaces in path, extra fields, all-zero hits), and Error (missing file, malformed DA lines).

Part of the coverage-core work per docs/design/coverage.org.

0 files changed, 0 insertions, 0 deletions