Keep progress inside the initiating Button/IconButton or centered within a
LoadingRegion without changing layout or unmounting live content. Document
ownership and completion/error behavior in the registry and living catalog.
Validation: qualified NET02 DG build/typecheck/registry/loading tests;
existing browser geometry, theme and error lifecycle acceptance. All eleven
committed files match the qualified source artifact byte for byte.
Codex
8c53f73ee5