commandEnvExecer.prepare rebuilt commands into a single shell string
using `fmt.Sprintf("%q", arg)`, which produces Go string literals, not
shell-quoted tokens. Go's %q does not escape `$`, backticks, or other
metacharacters that remain active inside double quotes, so an argument
such as `$(...)` was evaluated by the shell as command substitution.
Arguments flow from devcontainer config and workspace-folder, making
this exploitable.
Pass the command to the shell as positional parameters and run `"$@"` so
the shell forwards argv verbatim without re-parsing it.
The Windows previous handling is not required because Coder doesn't
support devcontainers on Windows, so it is removed.
Zach
112c921235