fix(hermes-code): add branch discovery trait to multibranch source

Indexing succeeded but discovered no branches without an explicit
gitBranchDiscovery trait, so hermes-repair/* never got a validation build.

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

services/jenkins/configmap-jcasc.yaml

@@ -456,6 +456,9 @@ data:
                     id('hermes-code-demo-branches')
                     remote('https://scm.bstein.dev/bstein/hermes-code-demo.git')
                     credentialsId('gitea-pat')
+                    traits {
+                      gitBranchDiscovery()
+                    }
                   }
                 }
               }