pty/run answers with the command's output; pin cloud9 with 9ns concurrency and E.BUSY

The answer is now the header line (exit N, or exit N cut M when only the
last 64 KiB were kept, or exit N cut when its start scrolled out of the
history), then what the command printed: the screen text between its C and
D marks, which the marks handler pins so scrolling keeps them.

Also from review: a plain /log open honours its offset until follow is
written, so tail -n and less work; whitespace-only run lines are refused.

cloud9 is pinned at 82d8152c: 9ns keeps up to 32 requests in flight per
mount so a waiting read no longer freezes the rest of it, and E.BUSY
replaces the errno pardes spelled locally.

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

1 files changed, 1 insertions, 0 deletions

diff --git a/test/fs.py b/test/fs.py
index d44f417d..b4b0315b 100644
--- a/test/fs.py
+++ b/test/fs.py
@@ -310,6 +310,7 @@ def run_file(binary):
                 assert time.monotonic() < deadline, 'the shell never reached a prompt'
                 time.sleep(.05)
             assert run(client, term, b'false\n') == b'exit 1\n'
+            assert run(client, term, b'printf "one\\ntwo\\n"\n') == b'exit 0\none\ntwo\n'  # then what it printed
             assert run(client, term, b'sh -c "exit 7"\n') == b'exit 7\n'
             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