When `tui_app_server` is enabled, shell commands in the transcript
render as fully quoted invocations like `/bin/zsh -lc "..."`. The
non-app-server TUI correctly shows the parsed command body.
Root cause:
The app-server stores `ThreadItem::CommandExecution.command` as a
shell-quoted string. When `tui_app_server` bridges that item back into
the exec renderer, it was passing `vec![command]` unchanged instead of
splitting the string back into argv. That prevented
`strip_bash_lc_and_escape()` from recognizing the shell wrapper, so the
renderer displayed the wrapper literally.
Solution:
Add a shared command-string splitter that round-trips shell-quoted
commands back into argv when it is safe to do so, while preserving
non-roundtrippable inputs as a single string. Use that helper everywhere
`tui_app_server` reconstructs exec commands from app-server payloads,
including live command-execution items, replayed thread items, and exec
approval requests. This restores the same command display behavior as
the direct TUI path without breaking Windows-style commands that cannot
be safely round-tripped.
This PR replicates the `tui` code directory and creates a temporary
parallel `tui_app_server` directory. It also implements a new feature
flag `tui_app_server` to select between the two tui implementations.
Once the new app-server-based TUI is stabilized, we'll delete the old
`tui` directory and feature flag.
