every.channel: sanitized baseline

docs/COVERAGE.md

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+# Coverage
+
+every.channel uses `cargo-llvm-cov` to produce formal coverage reports.
+
+## Run (Recommended: Nix)
+
+```sh
+direnv allow
+./scripts/coverage.sh
+```
+
+To run the unit-subset coverage (does not require FFmpeg headers):
+
+```sh
+./scripts/coverage.sh unit
+```
+
+Artifacts:
+
+- `tmp/coverage/workspace.lcov`
+- `tmp/coverage/workspace.summary.txt`
+- `tmp/coverage/workspace-html/index.html`
+
+## Run (Inside nix develop)
+
+If you are already in `nix develop`, you can use:
+
+```sh
+just cov-workspace
+just cov-workspace-html
+```