ConptyConnection has two different failure modes:
1. We failed to initialize the pseudoconsole or create the process
2. The process exited with an error code.
Until this commit, they were treated the same way: closeOnExit=always
would force the pane/tab to be destroyed. This was very bad in case 1,
where we would display a (possibly useful) error message and then
immediately close the window.
This was made even worse by the change in #10045. We removed
startingDirectory validation and promoted it to an error message (so
that we could eventually let the connection handle startingDirectory in
its own way.) This of course revealed that a number of users had set
invalid starting directories… and those users included some who set
closeOnExit to always. Boom: instant "terminal opens and crashes"¹
In this commit, we introduce detection for a connection that fails
before it's been established. When that happens, we will ignore the
user's closeOnExit mode.
¹ It only looks like a crash; it's actually _technically_ functioning
properly.
Closes#10225.
31d78dceb5