A pty/ctl winsize gives a terminal two rows at least, so it no longer reads busy for ever

A one-row pty loses the prompt's input mark as soon as the prompt wraps,
and busy detection never sees the shell idle again. Placement already
keeps a new terminal at tag + 2 rows; a winsize write now keeps the pty
at two. A pane dragged down to one body row keeps a one-row pty, since
a taller pty than the pane shows would put its cursor below the pane.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 7 insertions, 0 deletions

diff --git a/test/fs.py b/test/fs.py
index 8d16d718..45fdbc38 100644
--- a/test/fs.py
+++ b/test/fs.py
@@ -435,6 +435,13 @@ def run_file(binary):
             assert run(client, term, b'fi\n') == b'error not run\n'  # a syntax error runs nothing
             assert run(client, term, b"echo 'open\n") == b'error not run\n'  # nor does an open quote
             assert run(client, term, b'true\n') == b'exit 0\n'  # ...and the shell is clear after
+            # A pty asked for one row gets two: one loses the prompt's input
+            # mark, and the shell would read busy for ever.
+            client.write(f'/pane/{term}/pty/ctl', b'winsize 20 1\n')
+            time.sleep(.5)
+            assert run(client, term, b'true\n') == b'exit 0\n'
+            assert client.read(f'/pane/{term}/pty/ctl').split()[2] == b'2', client.read(f'/pane/{term}/pty/ctl')
+            client.write(f'/pane/{term}/pty/ctl', b'winsize 80 24\n')
             with Client(address) as other:
                 slow = []
                 waiter = threading.Thread(target=lambda: slow.append(run(other, term, b'sleep 1\n')), daemon=True)