Section block — accessibility

Keyboard

Defect (measured): a collapsible header cannot be operated by keyboard. .sb-h.sb-click is a plain <div onClick> — no role="button", no tabIndex, no key handler — so folding and unfolding is mouse-only, and the header has no focus state at all. The same is true of the collapsed preview .sb-peek.sb-click. The Stat tile shows the correct pattern (role="button" + tabIndex=0 + Enter/Space).
Actions in the header are real <button>s and are reachable by Tab.
Content inside the section behaves as it would anywhere else.

The title is a <span>, not a heading element, so the page's own heading structure is not disturbed — screens that need a heading level supply it.
The count is rendered by the count badge and read after the title.
The collapsible header exposes no aria-expanded, because it is not a control (see the defect above); once it becomes a button, the state has to come with it.
The gear (.sb-cfg) is a button with its own accessible name; it is revealed on hover or focus within the header. On a phone it is replaced by the „Rozložení sekcí" item of the page ⋮; the sheet rows are menuitemradio with aria-checked (visible = checked).

Header actions take the foundation ring from ds.css.
The collapsible header has no ring, because it is not focusable.
The hidden gear becomes visible on :focus-within, so tabbing to it does not leave the user pressing an invisible control.

Computed from packages/ui/src/tokens/tokens.css:

block title uses --h2 in --ink-500; sec title uses --h3 in --fg-secondary = 3.93:1 light, 6.20:1 dark — below AA for small text in light theme.
The action link and the count follow their own components.
The section has no background of its own; contrast comes from the surface it sits on.

Collapsible headers are mouse-only and have no focus state — the family's main accessibility gap.
The sec title sits below AA in light theme.
The gear is hidden until hover or focus, so its existence is not discoverable by reading alone.