First layer: AFC fault detection less sensitive

A large, slow first layer tripped AFC's buffer fault detection ("AFC NOT
FEEDING"). _FIRST_LAYER_FAULT_DETECTION ON=1 at the end of PRINT_START
sets first_layer_sensitivity (4: pause after 70 mm instead of 30 mm);
ON=0 restores the [AFC_buffer] config value. The slicer calls ON=0 at
the start of layer 2:
  {if layer_num == 1}_FIRST_LAYER_FAULT_DETECTION ON=0{endif}
_PRINT_CLEANUP calls it too, for prints that end in the first layer.
ON=0 only restores what ON=1 changed.

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

macros/print/print_start_end.cfg

@@ -249,6 +249,10 @@ gcode:
     # per-reading width compensation made the flow jump between 77 and 119%.
     # To use it again: SET_BDWIDTH NAME=fila_width_0 COMMAND=ENABLE_WIDTH
 
+    # A large, slow first layer can trip AFC's buffer fault detection
+    # ("AFC NOT FEEDING"); the slicer switches it back at layer 2
+    _FIRST_LAYER_FAULT_DETECTION ON=1
+
     RESPOND MSG="starting"
     _STATUS STATE=printing
 
@@ -304,6 +308,34 @@ gcode:
     {% if 'gcode_macro _PURGE_CHECK_CFG' in printer %}
     SET_GCODE_VARIABLE MACRO=_PURGE_CHECK_CFG VARIABLE=ignore_missing_sensor VALUE=False
     {% endif %}
+    _FIRST_LAYER_FAULT_DETECTION ON=0                ; a print that ended during the first layer
+
+# AFC buffer fault detection (filament_error_sensitivity, 0-10, higher =
+# pauses sooner) with its own value during the first layer.
+# ON=1 at the end of PRINT_START, ON=0 from the slicer's layer change G-code
+# at the start of layer 2 (OrcaSlicer, layer_num counts from 0):
+#   {if layer_num == 1}_FIRST_LAYER_FAULT_DETECTION ON=0{endif}
+# _PRINT_CLEANUP also calls ON=0. The normal value is read from the
+# [AFC_buffer] config; ON=0 only restores it if ON=1 changed it.
+[gcode_macro _FIRST_LAYER_FAULT_DETECTION]
+description: AFC filament fault detection with first_layer_sensitivity during the first layer (ON=1), back to the config value (ON=0)
+variable_buffer: "Turtle_1"
+variable_first_layer_sensitivity: 4   # 0-10: 0 = off, 4 = pause after 70 mm, 8 = after 30 mm
+variable_lowered: False
+gcode:
+    {% set key = "afc_buffer " ~ buffer|lower %}
+    {% set normal = printer.configfile.settings[key].filament_error_sensitivity|default(0)|float if key in printer.configfile.settings else 0 %}
+    {% if params.ON|default(1)|int %}
+        {% if normal > 0 and first_layer_sensitivity|float != normal %}
+            AFC_SET_ERROR_SENSITIVITY BUFFER={buffer} SENSITIVITY={first_layer_sensitivity}
+            SET_GCODE_VARIABLE MACRO=_FIRST_LAYER_FAULT_DETECTION VARIABLE=lowered VALUE=True
+            RESPOND MSG="AFC fault detection {first_layer_sensitivity} for the first layer (normally {normal})"
+        {% endif %}
+    {% elif lowered %}
+        AFC_SET_ERROR_SENSITIVITY BUFFER={buffer} SENSITIVITY={normal}
+        SET_GCODE_VARIABLE MACRO=_FIRST_LAYER_FAULT_DETECTION VARIABLE=lowered VALUE=False
+        RESPOND MSG="AFC fault detection back to {normal}"
+    {% endif %}
 
 # Retract/unretract that is remembered across prints and restarts.
 # Klipper's G10 only retracts once until a G11, and nothing sends G11 here,