fix(tmux): portable port probe, verify remote socket, doctor quoting

- deva.sh tmux setup/doctor: stock macOS has no coreutils timeout —
  probe port 22 with nc (present there), /dev/tcp fallback
- deva-tmux bridge (ssh): verify the remote tmux socket exists before
  forwarding — a tunnel to a missing socket reports up and then fails
  opaquely on every connection
- deva-tmux doctor: session count through the same sh -c positional
  pattern as every other remote invocation

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: lroolle

deva.sh

@@ -1309,6 +1309,16 @@ shorten_path() {
 # provisioning). The host side owns exactly what must not be done from
 # inside the sandbox: authorizing the ssh key and running the socat daemon.
 
+# Stock macOS ships no `timeout`; probe with nc (present there) and fall
+# back to /dev/tcp, which fails fast on a refused localhost connect.
+tmux_host_port22_open() {
+    if command -v nc >/dev/null 2>&1; then
+        nc -z -w 2 127.0.0.1 22 2>/dev/null
+    else
+        (exec 3<>/dev/tcp/127.0.0.1/22) 2>/dev/null
+    fi
+}
+
 tmux_host_setup() {
     local marker="deva-host-tmux"
     local pub=""
@@ -1335,7 +1345,7 @@ tmux_host_setup() {
         echo "undo: remove the '$marker' line from ~/.ssh/authorized_keys"
     fi
 
-    if timeout 3 bash -c 'exec 3<>/dev/tcp/127.0.0.1/22' 2>/dev/null; then
+    if tmux_host_port22_open; then
         echo "ok: sshd is listening on port 22"
     else
         echo "warning: sshd is not reachable on 127.0.0.1:22" >&2
@@ -1435,7 +1445,7 @@ tmux_host_doctor() {
     else
         echo "ssh keypair:     NONE (ssh-keygen -t ed25519)"
     fi
-    if timeout 3 bash -c 'exec 3<>/dev/tcp/127.0.0.1/22' 2>/dev/null; then
+    if tmux_host_port22_open; then
         echo "sshd port 22:    open"
     else
         echo "sshd port 22:    CLOSED (macOS: Sharing > Remote Login)"

scripts/deva-tmux

@@ -259,6 +259,10 @@ bridge_start() {
         bin=$(host_tmux_bin)
         remote_sock=$(host_tmux_socket "$bin")
         [[ -n "$remote_sock" ]] || die "cannot determine host tmux socket path"
+        # Forwarding to a missing remote socket "succeeds" and then every
+        # connection through it fails opaquely — verify the server first.
+        hssh "$(host_target)" "sh -c 'test -S \"\$0\"' $(printf '%q' "$remote_sock")" ||
+            die "no host tmux server socket at $remote_sock — start one on the host: tmux new -d"
         if [[ "$foreground" == true ]]; then
             echo "bridge (ssh, foreground): $BRIDGE_SOCK -> $(host_target):$remote_sock"
             exec ssh -o BatchMode=yes "${SSH_OPTS[@]}" -N -L "$BRIDGE_SOCK:$remote_sock" "$(host_target)"
@@ -389,7 +393,7 @@ cmd_doctor() {
                     local bin
                     if bin=$(host_tmux_bin 2>/dev/null); then
                         echo "host tmux:         $bin"
-                        echo "host sessions:     $(hssh "$target" "$bin ls 2>/dev/null | wc -l" | tr -d ' ')"
+                        echo "host sessions:     $(hssh "$target" "sh -c '\"\$0\" ls 2>/dev/null | wc -l' $(printf '%q' "$bin")" | tr -d ' ')"
                     else
                         echo "host tmux:         NOT FOUND on host"
                     fi