ci: fix nightly publishing on release/struts-6-8-x (#1644)

* ci: update Jenkinsfile branch guards from struts-6-7-x to struts-6-8-x

The Build Source & JavaDoc, Deploy Snapshot, and Upload nightlies stages
still referenced release/struts-6-7-x in their when conditions, causing
them to be skipped on every release/struts-6-8-x build. This prevented
6.9.0-SNAPSHOT artifacts from being published to nightlies.

Made-with: Cursor

* chore: add .metals, .bloop, and .vscode to .gitignore

Made-with: Cursor

.gitignore

@@ -49,3 +49,6 @@ test-output/
 
 # Claude Code specific local settings
 .claude/
+.metals/
+.bloop/
+.vscode/

Jenkinsfile

@@ -145,7 +145,7 @@ pipeline {
         }
         stage('Build Source & JavaDoc') {
           when {
-            branch 'release/struts-6-7-x'
+            branch 'release/struts-6-8-x'
           }
           steps {
             dir("local-snapshots-dir/") {
@@ -156,7 +156,7 @@ pipeline {
         }
         stage('Deploy Snapshot') {
           when {
-            branch 'release/struts-6-7-x'
+            branch 'release/struts-6-8-x'
           }
           steps {
             withCredentials([file(credentialsId: 'lukaszlenart-repository-access-token', variable: 'CUSTOM_SETTINGS')]) {
@@ -166,7 +166,7 @@ pipeline {
         }
         stage('Upload nightlies') {
           when {
-            branch 'release/struts-6-7-x'
+            branch 'release/struts-6-8-x'
           }
           steps {
             sh './mvnw -B package -DskipTests'