PA calibration reads Spoolman first; guard resets a sensor left in PA mode

- LANE_CALIBRATE_PA: when a calibration will run, assign the lane's spool
  again (SET_SPOOL_ID) so AFC reads the Spoolman temperature now; AFC
  only reads it at spool assignment and Klipper start (TPU calibrated at
  210C after Spoolman was set to 230C). The calibration moved to
  _LANE_CALIBRATE_PA_RUN, rendered after the refresh.
- bdp_guard: an emergency stop during PA_CALIBRATE leaves the sensor in
  PA mode (FIRMWARE_RESTART does not reset it). When arming, read the
  mode register and switch the sensor back to probe mode with a fresh
  baseline before watching it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

extras/bdp_guard.py

@@ -40,6 +40,9 @@
 
 import logging
 
+REG_MODE = 48         # status_clk: 7 = PA mode, 2 = probe (endstop) mode
+REG_RESET_PROBE = 52  # set_normal: write 1 = take the current reading as zero
+MODE_PA = 7
 REG_EXT = 54          # extension marker 0xBD + version
 REG_DELTA = 64        # chk_delta, int16 little-endian
 EXT_MAGIC = 0xBD
@@ -134,6 +137,31 @@ class BDPGuard:
             return False
         return len(data) == 2 and data[0] == EXT_MAGIC and data[1] >= 1
 
+    def _ensure_probe_mode(self, gcmd):
+        # An emergency stop during PA_CALIBRATE leaves the sensor in PA mode
+        # (FIRMWARE_RESTART does not reset it); bdpressure.py only switches
+        # it back at the next homing move, after the guard is armed. In PA
+        # mode the delta means nothing and could trip the guard. Register 48
+        # is the mode: 7 = PA, 2 = probe.
+        if getattr(self.sensor, 'last_state', 0):
+            return  # a calibration runs, leave the sensor alone
+        try:
+            mode = bytearray(self.i2c.i2c_read([REG_MODE], 1)['response'])
+            if len(mode) != 1 or mode[0] != MODE_PA:
+                return
+            self.sensor.set_probe_mode()
+            # new samples at the probe sample rate, then a fresh baseline
+            self.reactor.pause(self.reactor.monotonic() + 0.5)
+            self.i2c.i2c_write([REG_RESET_PROBE, 1])
+            self.reactor.pause(self.reactor.monotonic() + 0.3)
+        except Exception:
+            logging.exception("bdp_guard: switching the sensor to probe mode failed")
+            return
+        msg = ("BDP_GUARD: bd_pressure was still in PA mode (stopped "
+               "calibration?), switched to probe mode")
+        logging.info(msg)
+        gcmd.respond_info(msg)
+
     def _stop_timer(self):
         if self.timer is not None:
             self.reactor.unregister_timer(self.timer)
@@ -200,6 +228,7 @@ class BDPGuard:
                 gcmd.respond_info("BDP_GUARD_ARM: bd_pressure load-check "
                                   "extension not found, guard not armed")
                 return
+            self._ensure_probe_mode(gcmd)
         self.phase_mode = mode
         self._reset_phase(phase)
         self.armed_until = self.reactor.monotonic() + self.timeout