Spec clarification: TabId 0

[carlosjeurissen]

Currently it is unspecified if tabId 0 is a valid tab id or should be regarded as missing tab id (-1), as has happened in the past in Safari (see https://developer.apple.com/forums/thread/668159).

It would be helpful for developers and library maintainers to know if tab ids can be 0 or if this scenario existed in the past and in what APIs, so extensions know whether or not to regard them as either a valid tab id or as missing tab id.

[tophf]

Chrome never used 0, but Firefox definitely have been using it for many years last time I checked at least in Android.

[xeenon]

Safari/WebKit also never uses 0 as of Safari 18 at least. Any case of 0 would be considered a bug.