fix(codex-fleet-demo): guard attach behind TTY check, drop exec (#168)

up.sh ended with 'exec tmux attach' which replaces the calling shell with
tmux. When the script is launched without a controlling terminal (kitty
launcher, command picker, non-interactive shell, etc.), the attach
aborts with 'open terminal failed: not a terminal' and the parent
process is left in a broken state -- observed to lock up the kitty
session selector that spawned up.sh.

Guard the attach behind '[[ -t 0 && -t 1 ]]' and drop the 'exec' so the
shell returns cleanly whether or not the attach actually happens. When
no TTY is present, print the manual attach command and exit 0 normally.

Tear-down + re-up is the recovery path if you hit this in the wild.

Co-authored-by: NagyVikt <nagy.viktordp@gmail.com>

Author: NagyVikt

scripts/codex-fleet/demo/up.sh

@@ -210,6 +210,16 @@ echo "demo up. session=$SESSION socket=$SOCKET plan=$PLAN_SLUG"
 echo "attach: tmux -L $SOCKET attach -t $SESSION"
 echo "tear down: bash scripts/codex-fleet/demo/down.sh"
 
+# Attach only when stdin + stdout are real TTYs. Without that, `exec tmux
+# attach` aborts with "open terminal failed: not a terminal" and strands the
+# parent — observed to lock up the kitty launcher / session picker that
+# spawned up.sh. Drop `exec` so the shell returns cleanly even if tmux's
+# attach fails for some other reason. Print the attach command when we skip.
 if [[ "$attach" -eq 1 ]]; then
-    exec tmux -L "$SOCKET" attach -t "$SESSION"
+    if [[ -t 0 && -t 1 ]]; then
+        tmux -L "$SOCKET" attach -t "$SESSION"
+    else
+        echo "demo: no TTY available, skipping auto-attach" >&2
+        echo "      run from a terminal: tmux -L $SOCKET attach -t $SESSION" >&2
+    fi
 fi