[Accessibility]: History panel view: read out more user-friendly list summary on open

[lrhacker]

Audit type

Keyboard navigation

User journey audit issue

No response

Problem description

Similar to #44583, this is an improvement on the existing accessibility work done in #44452.

For this, per this comment from @courier-new:

[W]hen it starts reading the history, there's no way of knowing how long it will take to finish unless you see the whole list yourself. Could we consider having a <VisuallyHidden /> message with aria-live="polite" at the top of the ConnectionContainer that announces how many history items there are, or something similar, instead?

Expected behavior

Read out a more user-friendly summary message (or similar) when the history panel opens. If the work to manage the focus from #44583 has already been done, there might be other options, as well (e.g. read out a list summary, then focus and read out the first item to start with). It might be worth coordinating with design on the message that's read aloud.

Additional details

No response

Assigning labels

• Please give this issue an estimate by applying a label like estimate/Xd, where X is the estimated number of days it will take to complete.
• If this issue is specific to a specific Sourcegraph product, please assign the appropriate team label to this issue.
• If this issue will require input from designers in order to complete, please assign the label needs-design.
• If you are confident that this issue should be fixed by GitStart, please assign the label gitstart.

Owner

This issue will be fixed by my team, I have assigned a relevant member to it, or I will do so in the near future.

/cc @felixfbecker