docker: give the docker_exec console a tall default PTY geometry

The docker_exec console resized its exec PTY to 80x24 until a client
sent NAWS. CLIs that page on the PTY window size instead of the
terminal length (the IOS-XR pager) therefore parked long output at
--More-- for clients that never negotiate NAWS — netmiko, bare telnet —
making copilot device commands time out on XRd.

Default the exec to 511x10000 instead (511 matches netmiko's own
'terminal width 511' convention): no paging and no hard wrapping for
non-NAWS clients, while real NAWS clients keep resizing to their actual
geometry as before.

Also updates the project memory record with the confirmed root cause
and the fix.

tests/compute/docker/test_vendor_docker_vm.py

@@ -531,6 +531,17 @@ async def test_first_connect_creates_exec(compute_project, manager):
     srv._create_exec.assert_called_once()
 
 
+@pytest.mark.asyncio
+async def test_first_connect_sets_tall_default_pty_geometry(compute_project, manager):
+    """The exec PTY must start tall/wide: a 24-row initial geometry makes CLIs
+    that page on the PTY window size (IOS-XR pager) park at --More-- for
+    clients that never send NAWS (netmiko, bare telnet)."""
+
+    srv = _make_lazy_server(compute_project, manager)
+    await srv.client_connected_hook()
+    srv._on_naws.assert_called_once_with(511, 10000)
+
+
 @pytest.mark.asyncio
 async def test_reconnect_live_exec_not_recreated(compute_project, manager):
     """Reconnecting while the exec is alive must NOT recreate it."""