fix(ci): address Greptile review findings

- Remove undefined should_bump_version input from release.yml
- Fix Discord action variable expansion (single to double quotes)
- Add has_changes gate to changelog and test jobs
- Use unique heredoc delimiter to prevent collision with commit messages

.github/actions/discord-notify/action.yml

@@ -43,8 +43,8 @@ runs:
           TIMESTAMP="\"timestamp\": \"$(date -u +%Y-%m-%dT%H:%M:%SZ)\","
         fi
         
-        # Escape description for JSON
-        DESCRIPTION=$(echo '${{ inputs.description }}' | jq -Rs .)
+        # Escape description for JSON (use double quotes for variable expansion)
+        DESCRIPTION=$(echo "${{ inputs.description }}" | jq -Rs .)
         
         PAYLOAD=$(cat <<EOF
         {