These OSC 133 semantic prompt sequences mark the primary and secondary
parts of the prompt strings.
PS1 is marked as the primary (initial) prompt. This is the default, so
we could skip emitting these sequences, but they're added here for now
to be explicit and consistent with what other terminal emulators do in
their shell integrations.
If PS1 is a multiline prompt (i.e. it contains a newline), we mark the
last line as a secondary prompt (k=s). bash doesn't redraw the leading
lines of a multiline prompt on its own, so we can use this information
at runtime to prevent the preceding lines from being erased by ghostty
after a resize.
PS2 is always marked as a secondary prompt.
This change adds automatic bash shell detection and integration.
Unlike our other shell integrations, bash doesn't provide a built-in
mechanism for injecting our ghostty.bash script into the new shell
environment.
Instead, we start bash in POSIX mode and use the ENV environment
variable to load our integration script, and the rest of the bash
startup sequence becomes the responsibility of our script to emulate
(along with disabling POSIX mode).
This adds a new option to the shell integration feature set, `no-title`.
If this option is set, the shell integration will not automatically
update the window title.
