//! Kvasir — Unified Visual Computation Graph.
//!
//! See IMPLEMENTATION-PLAN.md for the full architecture. In short:
//! - Every render operation is a `KvasirNode` with typed resource I/O.
//! - `KvasirGraph` is a DAG of nodes connected by `ResourceId` edges.
//! - `ExecutionPlanner` derives correct order, barriers, and dead-node elimination.
//! - `ResourceRegistry` tracks GPU resource lifetimes.
use fmt;