Only provider delegates populated selectedTab, so activating Overview,
Usage & Spend or Sessions left it pointing at the provider tab that had
just been deselected. A later resize or tab-width change then scrolled
that stale provider back into view, hiding the tab the user had actually
picked.

Route selection through one claimSelectedTab(item, isSelected) on the
strip: a tab claims the slot when it becomes selected and releases it
when it stops being selected. Overview, the global tabs and the provider
tabs all report through it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>