refactor(system-commands): use string interactive spec so undercover instruments

`cj/system-cmd' had `(interactive (list (read-shell-command "System
command: ")))' -- the destructured-list interactive spec.  Undercover.el
relies on edebug instrumentation, which doesn't see past that form, so
the entire function body registered as 0 hits under coverage even
though tests call the function directly.

Switch to the equivalent string spec `(interactive "sSystem command: ")'.
Same UX (prompt, history, single-string result), but the body now
instruments correctly and coverage moves from 34/49 to 50/51.

Add one more test that captures the `run-at-time' lambda in
`cj/system-cmd-restart-emacs' and invokes it directly so the inner
`call-process-shell-command' branch registers, taking coverage to 51/51.

0 files changed, 0 insertions, 0 deletions