Function keys_binding 

pub fn keys_binding(component: &str) -> String

__KEYS_<C> — every instance key of C that has ever rendered, in first-render order.

★ IT EXISTS BECAUSE THE SWEEP MUST BE ITERABLE ON EVERY TIER. The seen-map answers “which pass was this instance last drawn in” in one lookup, but WALKING a map is not something the wasm backend lowers (“unsupported iteration over a non-sequence value”), and a sweep that ran on two tiers and not the third would be the exact shape this campaign exists to prevent. A sequence walks everywhere, so the keys live in one and the passes in the other.