Wait for shell prompt after 'Last login:' banner on fresh serial login

After sending the password, read_until_quiet returned as soon as the
'Last login:' banner went quiet — before the actual shell prompt arrived.
Since 'Last login:' proves the password was accepted, do a second read
(up to 10s) specifically to catch the delayed prompt.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

modules/workflow_serial.py

@@ -135,6 +135,15 @@ def _login_serial_console(ser: SerialPort) -> tuple:
         ok("Logged in to IOM console.")
         return True, password
 
+    # "Last login:" in the response confirms the password was accepted —
+    # the shell prompt just hasn't arrived yet (slow shell init or motd).
+    # Give it up to 10 more seconds to appear.
+    if "last login" in response.lower():
+        response += _ANSI_RE.sub("", ser.read_until_quiet(quiet_period=1.5, timeout=10.0))
+        if _at_shell_prompt(response):
+            ok("Logged in to IOM console.")
+            return True, password
+
     error(f"Login failed. Console response: {response.strip()[:120]}")
     return False, ""