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>

README.md

@@ -42,7 +42,7 @@ everything below, grouped by topic. Comment out what you do not use there.
 | `purge_until_empty.cfg` | `PURGE_UNTIL_EMPTY`: purges a snapped filament out until there is no more nozzle pressure | same as `purge_check.cfg` |
 | **pressure_advance/** | | |
 | `bd_pressure.cfg` | `[bdpressure bd_pa]` (I2C on the Nitehawk) and the vendor macros `PA_CALIBRATE`, `PA_E`, `PA_RESET`, `PA_STATE`; `PA_CALIBRATE` no longer sets Z back to a value read before the test (wrong after a Z hop in `G28 XY`) | `bdpressure.py` from the bd_pressure repo |
-| `bd_pa_spoolman.cfg` + `bd_pa_*.sh` | `LANE_CALIBRATE_PA`, `PA_CALIBRATE_ALL_LANES`, `LANE_RECAL_PA`, `SET_SPOOL_ID`, `PA_STATUS`: pressure advance per lane/spool, cached locally and in Spoolman; a calibration with no result, a pause during the test or too few/stuck sensor readings is rejected and not saved | bd_pressure, AFC, Spoolman, `gcode_shell_command` |
+| `bd_pa_spoolman.cfg` + `bd_pa_*.sh` | `LANE_CALIBRATE_PA`, `PA_CALIBRATE_ALL_LANES`, `LANE_RECAL_PA`, `SET_SPOOL_ID`, `PA_STATUS`: pressure advance per lane/spool, cached locally and in Spoolman; before a calibration the lane's spool is assigned again so a temperature just changed in Spoolman is used; a calibration with no result, a pause during the test or too few/stuck sensor readings is rejected and not saved | bd_pressure, AFC, Spoolman, `gcode_shell_command` |
 | **spoolman/** | | |
 | `active_spool.cfg` | `SET_ACTIVE_SPOOL`, `CLEAR_ACTIVE_SPOOL` | Spoolman in Moonraker |
 | **leds/** | | |
@@ -57,7 +57,7 @@ everything below, grouped by topic. Comment out what you do not use there.
 | `xy_drift.py` | `AFC_XY_SAFETY_CHECK`: measures lost XY steps from the stepper step counts at the endstop triggers (CoreXY). The toolhead position after homing cannot show lost steps. |
 | `bdwidth_status.py` | exposes bdwidth's motion counter and width to macros (`present: False` with neutral values when no bdwidth is configured, so the macros also work without it), and keeps a USB dropout of bdwidth (port: usb) from shutting down Klipper: the read is retried every 10 s and the port reopened |
 | `bdpressure_check.py` | bd_pressure load check (`BDP_CHECK_START/STOP/QUERY`). Needs the load-check firmware from the bd_pressure `load-check-extension` branch; on stock firmware it reports "not available" and does nothing. Also reports how many readings the last `PA_CALIBRATE` got (`pa_points`, `pa_distinct`), used to reject runs with a silent or stuck sensor. |
-| `bdp_guard.py` | nozzle collision guard: while armed (`BDP_GUARD_ARM/DISARM/QUERY`) reads the bd_pressure force every 20 ms over I2C and, in stop mode, shuts Klipper down when it stays above the threshold. Reports reads, peak and errors per phase in the console and klippy.log. Puts a lock on the sensor's I2C connection that `bdpressure.py` and `bdpressure_check.py` also go through (Klipper allows one I2C request at a time per device). Needs the load-check firmware. |
+| `bdp_guard.py` | nozzle collision guard: while armed (`BDP_GUARD_ARM/DISARM/QUERY`) reads the bd_pressure force every 20 ms over I2C and, in stop mode, shuts Klipper down when it stays above the threshold. Reports reads, peak and errors per phase in the console and klippy.log. When it arms and finds the sensor still in PA mode (an emergency stop during `PA_CALIBRATE`; `FIRMWARE_RESTART` does not reset the sensor), it switches it to probe mode and takes a new zero first. Puts a lock on the sensor's I2C connection that `bdpressure.py` and `bdpressure_check.py` also go through (Klipper allows one I2C request at a time per device). Needs the load-check firmware. |
 
 ### Scripts (`scripts/`)