feat: split runNodeTest into runNodeInstall + runNodeTest, add lcov to sonar

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

vars/runNodeInstall.groovy

@@ -0,0 +1,13 @@
+/**
+ * Runs npm install inside current container.
+ * Must be called inside container('node') block.
+ *
+ * config keys (all optional):
+ *   workDir - directory to run in, default: '.'
+ */
+def call(Map config = [:]) {
+    def workDir = config.workDir ?: '.'
+    dir(workDir) {
+        sh 'npm install'
+    }
+}