- 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>