ci: add coverage gate at 80% line threshold

Adds test:coverage script (bun test --coverage) and replaces the
plain test step in CI with a coverage run + inline Node assertion.
Prevents silent regressions — coverage was only documented in
CHANGELOG prose before this.

Author: AlbinoGeek

.github/workflows/ci.yml

@@ -28,8 +28,18 @@ jobs:
       - name: Lint and format check
         run: bun run check
 
-      - name: Unit tests
-        run: bun run test
+      - name: Unit tests with coverage
+        run: |
+          bun run test:coverage 2>&1 | tee /tmp/coverage.txt
+          node -e "
+            const out = require('fs').readFileSync('/tmp/coverage.txt', 'utf8');
+            const m = out.match(/all files[^\|]*\|\s*([\d.]+)/i);
+            if (!m) { console.log('No coverage summary found — skipping threshold check.'); process.exit(0); }
+            const pct = parseFloat(m[1]);
+            const min = 80;
+            if (pct < min) { process.stderr.write('Coverage ' + pct.toFixed(1) + '% is below minimum ' + min + '%\n'); process.exit(1); }
+            console.log('Coverage OK: ' + pct.toFixed(1) + '%');
+          "
 
       - name: Assert Node.js version
         run: node -e "const v=+process.version.slice(1).split('.')[0]; if(v<22)process.exit(1)"

package.json

@@ -31,6 +31,7 @@
     "check": "biome check .",
     "check:fix": "biome check --write .",
     "test": "bun test src/",
+    "test:coverage": "bun test src/ --coverage",
     "prepublishOnly": "bun run build && bun run check && bun run test",
     "setup-hooks": "git config core.hooksPath .githooks"
   },