Fix serial login detection when IOM is already logged in

Adds _at_shell_prompt() helper that detects a shell prompt by checking
whether any line ends with '#' or '# ', rather than using a bare '#' in
response check guarded by 'login' not in output. The old guard caused a
false negative when the IOM echoed 'Last login: ...' text alongside the
prompt, sending an unnecessary login attempt to an active session.

Also broadens _ANSI_RE to catch all CSI escape sequences and two-character
ESC sequences, not just the original five terminal codes.

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

modules/workflow_serial.py

@@ -26,8 +26,24 @@ from ui import (
     prompt, prompt_ip, prompt_yn, prompt_password,
 )
 
-# Strip ANSI escape sequences from serial terminal output
-_ANSI_RE = re.compile(r'\x1b\[[0-9;]*[mGKHF]')
+# Strip ANSI escape sequences from serial terminal output.
+# Catches CSI sequences (ESC[...X) and other two-character ESC sequences.
+_ANSI_RE = re.compile(r'\x1b(?:\[[0-9;]*[A-Za-z]|[^[])')
+
+
+def _at_shell_prompt(text: str) -> bool:
+    """
+    Return True if any line in text looks like a root shell prompt.
+    Checks whether a non-empty line ends with '#' or '# ' — the pattern
+    produced by prompts like 'root@hostname:~#' — without being tripped
+    up by the word 'login' appearing elsewhere in the output (e.g. in
+    'Last login: ...' messages shown after a session is resumed).
+    """
+    for line in text.splitlines():
+        stripped = line.rstrip()
+        if stripped.endswith("#") or stripped.endswith("# "):
+            return True
+    return False
 
 
 # ── Serial Redfish transport ───────────────────────────────────────────────────
@@ -35,7 +51,8 @@ def _login_serial_console(ser: SerialPort, password: str) -> bool:
     """
     Perform the root login sequence on the IOM serial console.
     Handles both the case where a login prompt is showing and where
-    a shell session is already active.
+    a shell session is already active (i.e. was never logged out after
+    a prior run — the IOM stays logged in until power-cycled).
     Returns True if a shell prompt is reached, False on failure.
     """
     info("Logging in to IOM serial console...")
@@ -43,13 +60,16 @@ def _login_serial_console(ser: SerialPort, password: str) -> bool:
     # Send a newline to get the current state of the console
     ser.send_line("", delay=0.5)
     response = _ANSI_RE.sub("", ser.read_until_quiet(quiet_period=0.5))
-    low = response.lower()
 
-    # Already at a shell prompt — no login needed
-    if ("#" in response or "$" in response) and "login" not in low:
+    # Already at a shell prompt — no login needed.
+    # Use _at_shell_prompt() rather than a bare '#' check so that
+    # 'Last login: ...' text in the response does not cause a false negative.
+    if _at_shell_prompt(response):
         ok("Already at shell prompt.")
         return True
 
+    low = response.lower()
+
     # Send username if we see a login prompt (or an empty/unknown response)
     if "login" in low or not response.strip():
         ser.send_line("root", delay=0.5)
@@ -60,7 +80,7 @@ def _login_serial_console(ser: SerialPort, password: str) -> bool:
         ser.send_line(password, delay=0.5)
         response = _ANSI_RE.sub("", ser.read_until_quiet(quiet_period=2.0))
 
-    if "#" in response or "$" in response:
+    if _at_shell_prompt(response):
         ok("Logged in to IOM console.")
         return True