Async state changes are announced and focus is managed — transient status via live regions without stealing focus; context replacements move focus to the revealed surface, never both for the same message

Requirement

Every async state change communicates through exactly one of two channels, chosen by what the change is:

• Transient status (saving indicator, success toast, background update): a live region (role="status" / aria-live) that announces without moving focus.
• Context replacement (a panel replacing the acting surface, an error that needs action): move keyboard focus to the revealed surface or its first actionable element. The focused element's content is voiced by the focus move itself — do NOT also mark it role="alert", or the same message announces twice.

Never both channels for the same message; never neither.

Rationale

Merges the accessibility checklist AA "Status messages" (announceable without focus) with the focus-movement gap caught twice in loop runs 1–2 (post-submit focus stranded on a hidden control; then a banner with role="alert" + programmatic focus announcing twice). The two failures are one design decision made badly: which channel does this state change use? This control forces the choice at plan time — CMP-3's state enumeration is where each state declares its channel.

Passes when

• Toast "Attendance submitted." is role="status", auto-dismissing, focus untouched.
• On submit success that hides the acting button, focus moves to the revealed panel's first actionable element.
• An error banner that requires action receives focus (tabindex="-1" + .focus()) and carries NO role="alert" — the focus move is the announcement.
• A background auto-save indicator updates a polite live region only.

Fails when

• Focus rests on a hidden/removed control after a state change (stranded focus).
• The same message is announced twice (live-region role AND programmatic focus).
• A state change is visually obvious but silent to AT (no live region, no focus).
• Focus is yanked for a transient message the user didn't act on (focus theft).

How to verify

Deterministic half — planned checks/async-states extension: for each state surface, assert (live-region role XOR focus-target wiring). Until built: verify manually via DOM inspection (document.activeElement after each transition) and label it so. Judgment half — the evaluator grades the channel choice per state: transient vs context-replacement, and quotes any double-channel message.