ci: improve drone test checks and coverage reporting

.drone.yml

@@ -7,6 +7,9 @@ steps:
   image: golang:1.25.8
   commands:
     - go get ./...
-    - go test ./...
+    - go vet ./...
+    - mkdir -p .build
+    - go test -v -coverprofile=.build/coverage.out ./...
+    - go tool cover -func=.build/coverage.out | tee .build/coverage.txt | awk '/^total:/ { gsub("%", "", $3); if ($3 + 0 < 80) { printf("Coverage %.1f%% is below 80%%\n", $3); exit 1 } }'
     - go install golang.org/x/vuln/cmd/govulncheck@latest
-    - govulncheck -v -json ./... > vulncheck.json
+    - govulncheck -json ./... > vulncheck.json

coverage

@@ -1 +0,0 @@
-mode: set