fix(gcode): restore BBL initial-filament PA emission removed in error

af59501f4a ("feat: firmware-agnostic per-tool PA emission for IMEX
parallel modes") inadvertently deleted the BBL-specific PA emission for
initial_non_support_extruder_id while adding IMEX per-tool PA support.
That deletion was scope creep into core BBL functionality and not part
of the IMEX feature.

Restore the original block verbatim. The new IMEX-parallel-modes PA
emission (per-secondary-tool, gated on m_imex_parallel_mode) is left
untouched — that's legitimately IMEX scope. BBL printers in non-IMEX
mode now get back the pre-PR initial-PA behavior.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/libslic3r/GCode.cpp

@@ -3169,6 +3169,13 @@ void GCode::_do_export(Print& print, GCodeOutputStream &file, ThumbnailsGenerato
             // mark the first filament used in print
             file.write_format(";VT%d\n", initial_extruder_id);
         }
+        // Orca: add missing PA settings for initial filament
+        if (m_config.enable_pressure_advance.get_at(initial_non_support_extruder_id)) {
+            file.write(m_writer.set_pressure_advance(m_config.pressure_advance.get_at(initial_non_support_extruder_id)));
+            // Orca: Adaptive PA
+            // Reset Adaptive PA processor last PA value
+            m_pa_processor->resetPreviousPA(m_config.pressure_advance.get_at(initial_non_support_extruder_id));
+        }
     }
 
     //flush FanMover buffer to avoid modifying the start gcode if it's manual.