## Summary
Fix `+new-window -e <command>` inheriting forced shell integration from
the running GTK application.
Arguments after `-e` are now marked as an explicit command that requires
shell detection. That marker is propagated with the existing command
override to the new surface for both the current `+new-window` and
`+new-tab` GTK paths. When the override is applied, forced shell
integration becomes `detect`; an explicit `none` remains disabled.
This is scoped to the GTK `-e` path. It does not change the generic
forced shell-integration behavior, so configured integration continues
to support shell executables with non-standard names.
Fixes#12378.
## Root cause
The GTK IPC path replaced `config.command` for the new surface but
retained the running application's `shell-integration` value. `termio`
therefore treated an arbitrary explicit command such as Vim as the
forced shell and appended shell-specific arguments.
## AI usage
I used Hermes Agent (with ChatGPT 5.6) to help inspect the codebase,
trace the GTK command path, and draft parts of the implementation and
test. I manually reviewed and edited the changes, validated the behavior
and test results, and understand the affected code paths.
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