Greetings,

tab-bar-tab-post-open-functions need to be called during tab-bar
initialization. Currently, a user's custom post-open functions are invoked
only for tabs created beyond the initial tab. This is a bug, in my view.

I've created the patch vs. this morning's master and should also benefit
Emacs 30. I've been running a patched copy against my daily-use 29.4 for a
bit and it works as expected.

-Stephane