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.

gns3server/compute/docker/vendor_docker_vm.py

@@ -504,7 +504,14 @@ class _LazyExecTelnetServer(AsyncioTelnetServer):
                     log.warning(f"{self._log_name}: failed to create exec: {exc}", exc_info=True)
                     raise
                 try:
-                    await self._on_naws(80, 24)  # initial size before NAWS
+                    # Tall/wide default geometry before any NAWS arrives: a
+                    # 24-row PTY makes CLIs that page on the PTY window size
+                    # (e.g. the IOS-XR pager) park at --More-- for clients
+                    # that never negotiate NAWS (netmiko, bare telnet).
+                    # Width 511 matches netmiko's 'terminal width 511'.
+                    # Real NAWS clients resize to their own geometry right
+                    # after connecting.
+                    await self._on_naws(511, 10000)
                 except Exception:
                     pass
             else: