Change default key bindings to capture full screen contents (write_screen_file)

[MadLittleMods]

The current default keybinding on Ctrl-Shift-J/Cmd-Shift-J utilize write_scrollback_file which only captures text that's scrolled off-screen. This can be confusing, as I would expect it to capture everything on and off-screen.

Per the docs, write_screen_file is the "Same as write_scrollback_file but writes the full screen contents" which is perfect to solve this problem and aligns exactly with the expected behavior.

This change addresses the friction that people have reported in the discussions below and specifically coming from the search scrollback feature discussion, where Ctrl-Shift-J/Cmd-Shift-J is one of the interim decent workarounds but then you also have to figure out the extra intricacy to use write_screen_file instead of write_scrollback_file.

Previous discussions:

• Improve naming of `write_screen_file`and `write_scrollback_file` #3652
• write_scrollback_file doesn't include what's on the current screen #3496
• write_scrollback_file doesn't work when there's just a screenful of text #4911
• Truncated history? #4390
• Ghostty's "Zero Config" Defaults #2363 (comment)
• Search scrollback #189 (comment)
• Action that writes both scrollback and active screen to file. #2040

Workaround

Before this PR is merged, you can achieve the same result by updating your Ghostty config:

.config/ghostty

# So we have more scrollback history (the size of the scrollback buffer in bytes)
scrollback-limit = 100000000

# The default keybindings use `write_scrollback_file` but that only includes what is
# offscreen. `write_screen_file` includes what's on screen and offscreen.
keybind = ctrl+shift+j=write_screen_file:paste
keybind = ctrl+shift+alt+j=write_screen_file:open

[mitchellh]

Thanks, I think this is a very reasonable change.