- ElkDiagramRenderer.getElkRoot(): add null guard to prevent NPE when node is null (SQ java:S2259) - WriteBuffer: add offerOrWarn() that logs when buffer is full instead of silently dropping data. ChunkAccumulator now uses this method so ingestion backpressure is visible in logs (SQ java:S899) Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>