The coverage target captures an initial zero-counter baseline so every compiled, instrumented translation unit remains in the denominator even before a test exercises it. Header and template lines appear only when the compiler emits counters through a real instantiation or API use; include-only placeholder tests establish inventory ownership and parsing in that test's include context, but do not create synthetic numeric line entries. The turnkey GCC coverage build excludes CUDA, so CUDA code requires a separate coverage workflow. Headers whose explicit instantiations must contribute counters are listed in tests/coverage/expected_coverage_records.txt. Before generating HTML, the coverage target verifies that every listed header survives the final filters with source, line, and function records; a missing or empty record fails the target.