fix: make ssh-keyscan non-fatal in deploy workflow

ssh-keyscan can fail transiently; since rsync already uses
StrictHostKeyChecking=no, the keyscan is best-effort only.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/deploy.yml

@@ -86,7 +86,7 @@ jobs:
           mkdir -p ~/.ssh
           echo "${{ secrets.SSH_PRIVATE_KEY }}" > ~/.ssh/deploy_key
           chmod 600 ~/.ssh/deploy_key
-          ssh-keyscan -p ${{ secrets.SSH_PORT }} ${{ secrets.SSH_HOST }} >> ~/.ssh/known_hosts 2>/dev/null
+          ssh-keyscan -p ${{ secrets.SSH_PORT }} ${{ secrets.SSH_HOST }} >> ~/.ssh/known_hosts 2>/dev/null || true
 
       - name: Deploy via rsync
         run: |