fix: fail CI job when validation finds issues

Add verdict step that writes PASS/FAIL to a file, with a follow-up
workflow step that exits 1 on FAIL. Previously validation reported
issues in comments but the job always succeeded.

.github/workflows/validate.yml

@@ -142,8 +142,30 @@ jobs:
             ---
             *Validated by plugin-dev + codeflash-agent checks*
             </step>
+
+            <step name="verdict">
+            If ANY step above found issues that need fixing, write FAIL:
+            Run: python3 -c "open('/tmp/validation-verdict','w').write('FAIL')"
+
+            If all steps passed with no issues, write PASS:
+            Run: python3 -c "open('/tmp/validation-verdict','w').write('PASS')"
+            </step>
           claude_args: '--model us.anthropic.claude-sonnet-4-6 --allowedTools "Agent,Read,Glob,Grep,Bash(gh pr diff*),Bash(gh pr view*),Bash(gh pr comment*),Bash(gh api*),Bash(git diff*),Bash(git log*),Bash(git status*),Bash(cat *),Bash(python3 *),Bash(jq *)"'
 
+      - name: Check validation verdict
+        if: always()
+        run: |
+          if [ ! -f /tmp/validation-verdict ]; then
+            echo "::warning::No validation verdict file — Claude may not have reached the verdict step"
+            exit 0
+          fi
+          verdict=$(cat /tmp/validation-verdict)
+          echo "Verdict: $verdict"
+          if [ "$verdict" = "FAIL" ]; then
+            echo "::error::Plugin validation found issues that need fixing"
+            exit 1
+          fi
+
   claude-mention:
     concurrency:
       group: claude-mention-${{ github.event.issue.number || github.event.pull_request.number || github.run_id }}