fix(workflows): use conditional job execution to prevent duplicate runs

Replace concurrency-based duplicate prevention with conditional job
execution that properly handles both internal and fork PRs.

The condition checks if it's a push event OR a PR from a fork,
preventing duplicate runs while still supporting external contributors.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: cuioss-oliver

.github/workflows/maven.yml

@@ -6,15 +6,11 @@ on:
   pull_request:
     branches: [main]
 
-# Prevent duplicate runs when pushing to a PR branch
-# The second run (usually pull_request) cancels the first (push)
-concurrency:
-  group: ${{ github.workflow }}-${{ github.ref }}
-  cancel-in-progress: true
-
 jobs:
   build:
-
+    # Run on push events, OR on pull_request only if from a fork
+    # This prevents duplicate runs: push handles internal branches, PR handles forks
+    if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name != github.event.pull_request.base.repo.full_name
     runs-on: ubuntu-latest
     strategy:
       matrix: