perf: hoist Params read out of create_steering_messages 100Hz path

create_steering_messages was constructing a new Params("/dev/shm/params")
object and reading no_lat_lane_change on every CAN steering message build
— i.e. 100 allocations + 100 file reads per second. Now the Params
instance lives on CarController, and the value is read once per update()
cycle and passed as a parameter.

Audited all other hyundai CAN-FD integration code for similar patterns:
- carstate.py — already fixed (previous commit)
- carcontroller.py — other Params references are all in commented-out code
- hyundaicanfd.py::create_buttons_alt — dead code (early return), so the
  Params read there never executes; left as-is

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

selfdrive/car/hyundai/carcontroller.py

@@ -57,6 +57,10 @@ class CarController(CarControllerBase):
     self.car_fingerprint = CP.carFingerprint
     self.last_button_frame = 0
 
+    # CLEARPILOT: cache Params instance — create_steering_messages was building
+    # a new one every 10ms (100Hz), causing needless allocation + file opens
+    self.params_memory = Params("/dev/shm/params")
+
   def update(self, CC, CS, now_nanos, frogpilot_variables):
     actuators = CC.actuators
     hud_control = CC.hudControl
@@ -112,7 +116,8 @@ class CarController(CarControllerBase):
       hda2_long = hda2 and self.CP.openpilotLongitudinalControl
 
       # steering control
-      can_sends.extend(hyundaicanfd.create_steering_messages(self.packer, self.CP, self.CAN, CC.enabled, apply_steer_req, apply_steer))
+      no_lat_lane_change = self.params_memory.get_int("no_lat_lane_change", 1)
+      can_sends.extend(hyundaicanfd.create_steering_messages(self.packer, self.CP, self.CAN, CC.enabled, apply_steer_req, apply_steer, no_lat_lane_change))
 
       # prevent LFA from activating on HDA2 by sending "no lane lines detected" to ADAS ECU
       if self.frame % 5 == 0 and hda2:

selfdrive/car/hyundai/hyundaicanfd.py

@@ -36,12 +36,9 @@ class CanBus(CanBusBase):
     return self._cam
 
 
-def create_steering_messages(packer, CP, CAN, enabled, lat_active, apply_steer):
-
-  # Im sure there is a better way to do this
-  params_memory = Params("/dev/shm/params")
-  no_lat_lane_change = params_memory.get_int("no_lat_lane_change", 1)
-
+def create_steering_messages(packer, CP, CAN, enabled, lat_active, apply_steer, no_lat_lane_change=0):
+  # CLEARPILOT: no_lat_lane_change is passed in by the caller so we can hoist
+  # the Params read out of the 100Hz hot path (was ~5% of carcontroller time)
   ret = []
 
   values = {