Purge check: accept load-check firmware v2; chamber load levels first

- bdpressure_check.py accepted only extension version 1. The sensor now
  runs firmware version 2 (bytes 54-65 unchanged, diagnostics added), so
  every purge check reported bd_pressure as not answering. Accept 1 and 2.
- _LOAD_FOR_CHAMBER: the Blobifier only purges with the QGL applied, so
  the load before the chamber soak skipped its purge (0.0 mm extruded).
  Level the gantry and home Z first when the QGL is not applied.

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

macros/print/print_start_end.cfg

@@ -108,6 +108,16 @@ gcode:
         {% else %}
           RESPOND MSG="Chamber heating: loading and purging {ns.lane} ({new.material}, {tool}) before the chamber heats"
         {% endif %}
+        # The Blobifier only purges with the QGL applied: without it AFC
+        # loaded the lane and skipped the purge. Level now (PRINT_START
+        # levels again on the soaked bed) and home Z after it.
+        {% if printer.quad_gantry_level and not printer.quad_gantry_level.applied %}
+          _GUARD_ON PHASE=warmup_qgl
+          QUAD_GANTRY_LEVEL
+          _GUARD_ON PHASE=warmup_z_home
+          G28 Z
+          _GUARD_OFF
+        {% endif %}
         M109 S{temps|max}
         {tool}
         _LOAD_FOR_CHAMBER_VERIFY LANE={ns.lane}