CVE-2026-44646: LiquidJS's `{% render %}` tag silently bypasses per-render `ownPropertyOnly:true` via `Context.spawn()`

Context.spawn() in liquidjs creates a child Context for the {% render %} tag but does not propagate the parent context’s resolved ownPropertyOnly value. The new context re-derives ownPropertyOnly from opts.ownPropertyOnly (the instance-level option), silently discarding any RenderOptions.ownPropertyOnly override that was supplied to parseAndRender(). As a result, a developer who runs a Liquid instance with the backwards-compatible ownPropertyOnly:false and then locks down an untrusted render with parseAndRender(..., { ownPropertyOnly: true }) still leaks prototype-chain properties from inside any {% render %} partial. This is a distinct exploit surface from the previously identified array-filter variants (where, reject, group_by, find, find_index, has) — the underlying root cause in Context.spawn() is shared, but {% render %} is a separately reachable sink that needs no filter usage.