//! strop editor engine: documents, grammar dispatch, services, sessions — no
//! terminal. The binary (`crates/strop`) owns the physical terminal, cell-grid
//! rendering, the CLI, self-update, bench and headless frame rendering; it
//! drives this engine and injects frame capture at the composition roots.
// VF19 native mutant seams (verification/mutants.json): calibration only,
// compiled under `--cfg strop_mutant`, never in release artifacts.