fix: prevent duplicate enhancement guide runs per issue

When an issue is created with the 'enhancement' label, both the
'opened' and 'labeled' events fire, triggering the workflow twice.

Fix with two layers:
- concurrency group per issue number with cancel-in-progress
- refined if condition: 'labeled' only triggers when the specific
  label added is 'enhancement', not for any label change

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ako

.github/workflows/ai-enhancement-guide.yml

@@ -4,14 +4,21 @@ on:
   issues:
     types: [opened, labeled]
 
+concurrency:
+  group: enhancement-guide-${{ github.event.issue.number }}
+  cancel-in-progress: true
+
 permissions:
   issues: write
   contents: read
 
 jobs:
   guide:
-    # Only run for issues with 'enhancement' label
-    if: contains(github.event.issue.labels.*.name, 'enhancement')
+    # On 'opened': run if issue has 'enhancement' label
+    # On 'labeled': run only if the label just added is 'enhancement'
+    if: >-
+      (github.event.action == 'opened' && contains(github.event.issue.labels.*.name, 'enhancement'))
+      || (github.event.action == 'labeled' && github.event.label.name == 'enhancement')
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v5