Read the metadata prefix in staged geometric reads so one oversized metadata field no longer forces a full re-parse of the whole sidecar.
Co-authored-by: rodrigogs <rodrigogs@users.noreply.github.com>
_syncSidebarAria set aria-expanded on the newly-active rail button without
unsetting the previous one, so chat -> kanban -> skills left three buttons all
claiming aria-expanded=true. A screen reader announced three open disclosures
when only one panel owns the sidebar.
Reset every rail button that carries the attribute before setting the active
one.