Handle job-control signals and clear tostop

Prevent terminal job-control signals from suspending the script during recovery by trapping TSTP, TTIN and TTOU (instead of only TSTP) and restoring them on exit. Also clear the terminal 'tostop' flag in stop_spinner() with `stty -tostop` to avoid background spinner I/O from stopping the process group.

misc/core.func

@@ -607,6 +607,7 @@ stop_spinner() {
 
   unset SPINNER_PID SPINNER_MSG
   stty sane 2>/dev/null || true
+  stty -tostop 2>/dev/null || true
 }
 
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