Command line "-F" (fullscreen) should work in an already running instance

WindowsTerminal 1.21.2408.23001

In an already-running WT, this command splits the current pane and focuses the old one.

`wt sp -p TCC33 -V ; move-focus left`

This command does the same thing, not making it fullscreen.

`wt -F sp -p TCC33 -V ; move-focus left`

Is that as expected?

Start by reproducing both commands in an already-running Windows Terminal instance and compare how the `-F` option is handled. Trace the command-line handling for `wt -F` and verify completion when the existing instance becomes fullscreen while preserving the requested split and focus behavior.

Written by the indexing model from the issue text.