Announce steering divider to screen readers

[Copilot]

Steering is currently indicated visually in chat, leaving screen reader users without feedback. This adds a polite ARIA status announcement when the steering divider first appears so the same state change is conveyed audibly.

• Accessibility announcement
  • Emit a status() message when steering first appears (divider shown).

if (announceSteering && steeringCount > 0 && lastSteeringCount === 0) {
	status(localize('chat.pendingRequests.steeringQueued', "Steering"));
}

Original prompt

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This section details on the original issue you should resolve

<issue_title>when steering occurs, we indicate this visually, but not to screen reader users</issue_title>
<issue_description>We should use aria.status to indicate this</issue_description>

Comments on the Issue (you are @copilot in this section)

@meganrogge When a request is sent mid chat response, we call that steering and show that indicator visually

• Fixes when steering occurs, we indicate this visually, but not to screen reader users #295240

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[meganrogge]

@copilot we want steering to be announced when steering is shown visually, ensure that occurs. maybe use alert

[Copilot]

@copilot we want steering to be announced when steering is shown visually, ensure that occurs. maybe use alert

Updated the steering announcement to fire only when the steering divider first appears (keeping the ARIA status behavior). Commit: c35f63c. No UI changes to screenshot.

[Copilot]

Pull request overview

This PR adds accessibility support for steering notifications in the chat interface. When a chat request is sent mid-response (called "steering"), the change is currently only indicated visually via a divider. This update ensures screen reader users receive the same feedback through an ARIA status announcement.

Changes:

• Added ARIA status announcement using status() when steering first appears
• Track steering count transitions to announce only when going from 0 to >0 steering requests