Fix flaky CustomerServiceTest timing and migrate Sonar action

- Relax the virtual-threads timing assertion from 1.5s to 5s: the
  point is concurrent (~1s) vs sequential (~500s), and the tight
  bound failed intermittently on Windows CI runners
- Replace deprecated SonarSource/sonarcloud-github-action@master
  with SonarSource/sonarqube-scan-action@v8

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: kousen

.github/workflows/sonar.yml

@@ -32,8 +32,8 @@ jobs:
           restore-keys: ${{ runner.os }}-gradle
       - name: Build
         run: ./gradlew build jacocoTestReport --info
-      - name: SonarCloud Scan
-        uses: SonarSource/sonarcloud-github-action@master
+      - name: SonarQube Scan
+        uses: SonarSource/sonarqube-scan-action@v8
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           SONAR_TOKEN: ${{ secrets.SONAR_TOKEN }}

src/test/java/com/kousenit/virtualthreads/CustomerServiceTest.java

@@ -37,10 +37,12 @@ void testFetchCustomerData() {
         assertEquals("Customer 500", lastCustomer.name(), "Last customer name should match");
         assertEquals("customer500@example.com", lastCustomer.email(), "Last customer email should match");
 
-        // Check if the execution time is close to 1 second (allowing some margin)
+        // 500 concurrent 1-second calls should take about 1 second total,
+        // not the ~500 seconds a sequential version would need. The generous
+        // upper bound keeps this stable on slow CI runners.
         long executionTime = endTime - startTime;
-        assertTrue(executionTime >= 1000 && executionTime < 1500,
-                "Execution time should be close to 1 second, but was " + executionTime + " ms");
+        assertTrue(executionTime >= 1000 && executionTime < 5000,
+                "Execution time should be ~1 second (concurrent), but was " + executionTime + " ms");
         System.out.println("Execution time: " + executionTime + " ms");
     }