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

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

vars/runNodeTest.groovy

@@ -1,5 +1,5 @@
 /**
- * Runs npm install + npm test inside current container.
+ * Runs npm test inside current container. Expects npm install already done.
  * Must be called inside container('node') block.
  *
  * config keys (all optional):
@@ -11,7 +11,6 @@ def call(Map config = [:]) {
     def testCmd = config.testCmd ?: 'test'
 
     dir(workDir) {
-        sh 'npm install'
         sh "npm ${testCmd}"
     }
 }