v0.15.2

Release 0.15.2: keyed reconciliation in patch-children. In-place children stay attached; only changed positions move via insert-before; dropped children are pruned explicitly. Fixes focus loss across renders and cuts per-render DOM churn (folder nav 111 -> 4 mutations). Requires sigil 0.17.16 for the wasm-dom insert-before / remove-child primitives.