PA_CALIBRATE_ALL_LANES: skip lanes without filament

Lanes whose AFC prep and load sensors do not both see filament are
skipped with a message, as are names that are not AFC lanes. The
"complete" message is now a RESPOND, so it appears after the
calibrations instead of before them.

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

macros/pressure_advance/bd_pa_spoolman.cfg

@@ -557,11 +557,18 @@ gcode:
     {action_respond_info("PA_CALIBRATE_ALL_LANES starting for: %s" % raw_lanes)}
     {% for lane in lane_list %}
         {% set lane = lane.strip() %}
-        {% if lane != "" %}
+        {% set obj = "AFC_stepper " ~ lane %}
+        {% if lane == "" %}
+        {% elif obj not in printer %}
+            RESPOND MSG="PA_CALIBRATE_ALL_LANES: {lane} is not an AFC lane, skipped"
+        {% elif not (printer[obj].prep and printer[obj].load) %}
+            RESPOND MSG="PA_CALIBRATE_ALL_LANES: {lane} has no filament loaded, skipped"
+        {% else %}
             LANE_CALIBRATE_PA LANE={lane} FORCE={force}
         {% endif %}
     {% endfor %}
-    {action_respond_info("PA_CALIBRATE_ALL_LANES complete.")}
+    # RESPOND runs in order, after the calibrations above
+    RESPOND MSG="PA_CALIBRATE_ALL_LANES complete."
 
 
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