Synonym for `aria-live="off"` that is less confusing to authors

[patrickhlauke]

Description of bug or feature request

In a similar vein to precedents set by role="presentation"/role="none" and role="img"/role="image", I'd love to see some kind of synonym for the off value of aria-live. This would be a nice one to do in parallel with #2653

Many developers are still confused by the fact that off doesn't actually mean "this isn't a live region", but that it has this special "it IS actually a live region, but only announced when the user's focus/regard/cursor is on/in that element" meaning. This was one of the take-aways that came out of https://tetralogical.com/blog/2024/05/01/why-are-my-live-regions-not-working/ (when I actually had to go and edit MDN to clarify this very aspect, as MDN had documented it wrong as well).

I understand that trying to find a good synonym for this particular thing is hard. A naive aria-live="focus" is probably too loaded and incorrect a term, as it's not necessarily just about focus, and certainly not just focus on the element itself but also inside it. The exact best name for the synonym may need some wordsmithing/bikeshedding, but anything may be clearer than off and the confusion this caused/stil causes for developers. aria-live="current" ... or is that too close to aria-current? something more abstract like aria-live="context"?

Will this require a change to CORE-AAM?

Yes

Will this require a change to the ARIA authoring guide?

Possibly yes (don't think there's actually any good standalone examples of live regions at the moment in the APG, which is also a gap that should really be filled ... as quirks such as "in most cases, make sure the element exists in the DOM before you populate it" would be good to have some authoritative examples for.