fix: keep systemd's OSC 3008 shell context out of command output (#41)

Backport of the 0.15.1 fix onto 0ba5081, the commit netOrk pins, which
cannot take 0.15.x before it moves to napalm-device-types 4.22.

systemd 258 (Ubuntu 26.04) ships /etc/profile.d/80-systemd-osc-context.sh:
an interactive bash wraps every command in OSC 3008 sequences from PS0 and
PROMPT_COMMAND, each with a fresh UUID. They ended up in every value read
through netmiko's shell, and because the prompt never looked the same twice,
the prompt line stayed in the output too. os_version grew past 255
characters and netOrk could not store the poll.

The session now unsets PS0 and PROMPT_COMMAND right after switching the
history off and reads its prompt anew; _send() strips terminal codes from
what it returns.

napalm_linux/linux.py

@@ -167,6 +167,12 @@ _PRIVILEGED_STDIN = (
 #: a shell without ``set -o history`` (dash) only complains, to /dev/null.
 _HISTORY_OFF = " unset HISTFILE; set +o history 2>/dev/null; true"
 
+#: Sent right after ``_HISTORY_OFF`` (#41): systemd 258's
+#: ``/etc/profile.d/80-systemd-osc-context.sh`` wraps every command in OSC 3008
+#: sequences from ``PS0`` and ``PROMPT_COMMAND``, each with a fresh UUID. It appends
+#: to ``PROMPT_COMMAND`` as an array, so only ``unset`` removes its hook.
+_PROMPT_HOOKS_OFF = " unset PS0 PROMPT_COMMAND; true"
+
 #: First in every script ``_sudo`` runs: a sudo that does not prompt (NOPASSWD,
 #: a cached timestamp) leaves the password on stdin, and nothing may read it.
 _NO_STDIN = "exec </dev/null; "
@@ -398,6 +404,15 @@ class LinuxDriver(
         except Exception:
             logger.debug("Could not switch the shell history off on %s", self.hostname, exc_info=True)
 
+        # No systemd OSC 3008 context around every command (#41). netmiko learned
+        # the prompt with those sequences in front, and a prompt carrying a fresh
+        # UUID never matches again, so it reads the prompt anew once they are gone.
+        try:
+            self._device.send_command(_PROMPT_HOOKS_OFF, expect_string=_PROMPT_RE)
+            self._device.set_base_prompt()
+        except Exception:
+            logger.debug("Could not switch the prompt hooks off on %s", self.hostname, exc_info=True)
+
         # Prevent PTY from wrapping long output lines (e.g. docker JSON).
         try:
             self._device.send_command("stty cols 10000 2>/dev/null || true", expect_string=r"[#$>]\s*$")
@@ -430,15 +445,16 @@ class LinuxDriver(
     # ------------------------------------------------------------------
 
     def _send(self, command: str, read_timeout: float = 100) -> str:
-        """Send a command and return stripped output."""
+        """Send a command and return its output without terminal codes, stripped."""
         if not self._device:
             raise ConnectionClosedException("Not connected")
-        return self._device.send_command(
+        output = self._device.send_command(
             command,
             read_timeout=read_timeout,
             cmd_verify=False,
             expect_string=_expect_for(command),
-        ).strip()
+        )
+        return strip_terminal_codes(output).strip()
 
     def _sudo(self, command: str, read_timeout: float = 100) -> str:
         """Run *command* as root and return its output, stdout and stderr together.