fix(ci): schedule coordinator on builder agents

Jenkinsfile

@@ -45,7 +45,7 @@ def downstreamJobPrefixForJob(String jobBaseName) {
 
 pipeline {
     // 总控流水线只识别变更并调度独立的服务 Job；实际 Maven、镜像和部署在 Jenkinsfile.service 中完成。
-    agent any
+    agent { label 'java-builder' }
 
     options {
         disableConcurrentBuilds()

scripts/controller-pipeline-contract.test.mjs

@@ -5,6 +5,11 @@ import test from 'node:test'
 const pipeline = (await readFile(new URL('../Jenkinsfile', import.meta.url), 'utf8'))
   .replaceAll('\r\n', '\n')
 
+test('coordinator runs only on the shared Java builder pool', () => {
+  assert.match(pipeline, /agent \{ label 'java-builder' \}/)
+  assert.doesNotMatch(pipeline, /agent any/)
+})
+
 test('AUTO detects database migrations without expanding them to all services', () => {
   assert.match(pipeline, /def databaseMigrationPaths = \['deploy\/sql\/'\]/)
   assert.match(pipeline, /!databaseMigration && commonPaths\.any/)