chore: add local test coverage via cargo-llvm-cov

.gitignore

@@ -1,4 +1,8 @@
 /target
+
+# Coverage artifacts (cargo-llvm-cov)
+/lcov.info
+
 *.swp
 *.swo
 *~

CLAUDE.md

@@ -15,6 +15,7 @@ This project uses a `Makefile` as the **single source of truth** for build, form
 - `make build` — `cargo build --all-targets`
 - `make check` — `fmt-check` + `lint` + `test` (run this before declaring work done or pushing)
 - `make all` — `fmt` + `check` + `build`
+- `make coverage` — local test-coverage summary via `cargo-llvm-cov` (also `coverage-html` / `coverage-lcov`; on-demand, not a CI gate, not part of `make check`)
 
 ### Required workflow before finishing any code change
 

Makefile

@@ -1,4 +1,4 @@
-.PHONY: help fmt fmt-check lint test build build-release check all
+.PHONY: help fmt fmt-check lint test build build-release check all coverage coverage-html coverage-lcov
 
 CARGO ?= cargo
 
@@ -12,6 +12,9 @@ help:
 	@echo "  build-release - cargo build --release"
 	@echo "  check      - fmt-check + lint + test (run before pushing)"
 	@echo "  all        - fmt + check + build"
+	@echo "  coverage      - test coverage summary in the terminal (cargo-llvm-cov)"
+	@echo "  coverage-html - generate an HTML coverage report under target/llvm-cov/html"
+	@echo "  coverage-lcov - emit lcov.info for external tooling"
 
 fmt:
 	$(CARGO) fmt --all
@@ -34,3 +37,12 @@ build-release:
 check: fmt-check lint test
 
 all: fmt check build
+
+coverage:
+	$(CARGO) llvm-cov --all-targets
+
+coverage-html:
+	$(CARGO) llvm-cov --all-targets --html
+
+coverage-lcov:
+	$(CARGO) llvm-cov --all-targets --lcov --output-path lcov.info