feat(preview-tui): handle quoting in start_preview more robustly
This commit makes the script more resistant to naughty filenames.
The script now depends on bash for the following features:
- Arrays
Correctly creating and passing argument lists is now simple
- Parameter transformation
`${parameter@Q}` makes it easy to correctly quote a string so that it
can be safely re-evaluated by the interpreter later.
On iTerm, the shell command used to render the preview is now passed to
osascript via a named pipe: `$FIFO_OSASCRIPT`. By not embedding the
shell command directly, we now no longer need to worry about osascript's
quoting rules. It's not perfect, because $SHELL and $TMPDIR might
contain naughty characters, but it's quite unlikely to happen.