dev-inf: Add PR comment when bugs are detected

Adds a step to post a PR comment when Stage 3 confirms potential bugs.
The comment uses cautious language and links to the workflow run for
detailed findings.

Epic: none
Release note: none

Author: ajstorm

.github/workflows/pr-analyzer-threestage.yml

@@ -214,4 +214,21 @@ jobs:
             2. The final determination (critical bug found or no critical bugs)
             3. If bugs were found, what actions are recommended
 
-            **If all three stages detected bugs**, this indicates a potential issue that warrants investigation.
+            **If all three stages detected bugs**, this indicates a potential issue that warrants investigation.
+
+      - name: Comment on PR if bugs confirmed
+        if: contains(steps.stage3_result.outputs.result, 'STAGE3_RESULT: POTENTIAL_BUG_CONFIRMED')
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          gh pr comment ${{ github.event.pull_request.number }} --body "## Potential Bug(s) Detected
+
+          The three-stage Claude Code analysis has identified potential bug(s) in this PR that may warrant investigation.
+
+          **Analysis Results:**
+          - ⚠️ Stage 1 (Initial Screening): Potential bugs detected
+          - ⚠️ Stage 2 (Database Expert Review): Potential bugs not ruled out
+          - ⚠️ Stage 3 (Principal Engineer Review): Potential bugs not ruled out
+
+          **Next Steps:**
+          Please review the detailed findings in the [workflow run](${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }})."