fix job control on FreeBSD and macOS: do not use WCONTINUED

Go's syscall.WaitStatus decodes the "continued" status wrongly on BSD:
on FreeBSD it is read as killed by SIGCONT, so after bg the job was
reported as "Exit 147" and removed from the job table while it was
still running (fg: "no such job"); on macOS it is read as stopped.

The shell marks jobs as running itself when it continues them, so wait4
is called without WCONTINUED and only exited/signaled statuses finish a
process.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

jobs.go

@@ -162,9 +162,7 @@ func (j *job) update(pid int, ws syscall.WaitStatus) {
 		switch {
 		case ws.Stopped():
 			p.stopped = true
-		case ws.Continued():
-			p.stopped = false
-		default:
+		case ws.Exited() || ws.Signaled():
 			p.finished, p.stopped = true, false
 			p.err = waitStatusError(ws)
 			p.cmd.Process.Release()
@@ -185,17 +183,30 @@ func waitStatusError(ws syscall.WaitStatus) error {
 	return nil
 }
 
-// wait waits until no process of the job is running any more (all finished
-// or, with job control, stopped). With nohang it only collects the status
-// changes that are already available and does not block.
-func (j *job) wait(nohang bool) {
+// waitFlags returns the options for wait4: WUNTRACED to see stopped
+// processes (with job control) and WNOHANG to not block.
+//
+// WCONTINUED is not used: Go's syscall.WaitStatus decodes the "continued"
+// status wrongly on FreeBSD (as killed by SIGCONT) and macOS (as stopped).
+// The shell marks jobs as running itself when it continues them (fg, bg); a
+// job continued from outside (kill -CONT) stays "Stopped" in the job table
+// until it stops again or exits.
+func waitFlags(j *job, nohang bool) int {
 	flags := 0
 	if jobControl && j.pgid != 0 {
-		flags |= syscall.WUNTRACED | syscall.WCONTINUED
+		flags |= syscall.WUNTRACED
 	}
 	if nohang {
 		flags |= syscall.WNOHANG
 	}
+	return flags
+}
+
+// wait waits until no process of the job is running any more (all finished
+// or, with job control, stopped). With nohang it only collects the status
+// changes that are already available and does not block.
+func (j *job) wait(nohang bool) {
+	flags := waitFlags(j, nohang)
 
 	for {
 		// With job control all processes of the job are in its process