Add audit/ with 8 named CVE regression checks against doos

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

Makefile

@@ -4,7 +4,7 @@
 BUILD ?= build
 DOOS  := $(BUILD)/doos
 
-.PHONY: help build test check-docs bench charts docs release clean
+.PHONY: help build test audit check-docs bench charts docs release clean
 
 help: ## list the targets
 	@grep -hE '^[a-z-]+:.*##' $(MAKEFILE_LIST) | sed -E 's/:.*## /\t/' | column -t -s "$$(printf '\t')"
@@ -16,6 +16,9 @@ build: ## configure and compile into build/
 test: build ## end-to-end suite (real downloads, needs network, pasta, gpg, cgroup v2)
 	tests/run.sh $(DOOS)
 
+audit: build ## run the CVE regression checks under audit/ against build/doos (concurrent, -j)
+	$(MAKE) -C audit -j8 test DOOS=$(abspath $(DOOS))
+
 check-docs: ## every document links to every other, every relative link resolves
 	scripts/check-docs.sh