ee2c52bbc6
Add an optional renderContent field to canvas nodes across the go-zero API type, domain node, SQLC models/queries, PostgreSQL schema, and mappers so a lightweight transparent-WebP display texture persists alongside the original content. Prefer renderContent for project thumbnails and main-canvas previews, and treat both content and renderContent as protected/deletable asset URLs during canvas asset cleanup. Extend round-trip coverage. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>