Instrument each emitted statement with a per-source-line hit counter, gated
behind a new --coverage flag (default off) so ordinary builds — and the
compiler's own self-compile — stay byte-identical and the C-free bootstrap
fixpoint is untouched. A static line table plus a parallel hit-counter array
are dumped at exit through an atexit hook to $LUDIC_COVERAGE (default
ludic.cov) as a `FILE <name>` header and `<line> <hits>` rows.
bin/x test --coverage compiles the test specs with instrumentation, runs them
into per-file dumps, and aggregates a clean per-file line-coverage report that
names the unreached lines. Adds examples/library/coverage.ludic (a spec whose
tests deliberately miss one branch) and docs. Closes the last open acceptance
item of the testing framework (#12).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
