补齐刀补下模式切换错误覆盖

结论：基于 LinuxCNC interp_convert.cc convert_control_mode()、convert_coordinate_system() 和 convert_home()，native/source-link 现在覆盖刀补打开时 G64、G55、G28 被拒绝的失败分支。

test-linuxcnc-source-link.sh

@@ -1454,6 +1454,26 @@ fi
 grep -q "Cannot change tool offset with cutter radius compensation on" \
     "$output_dir/cnc_sim_linuxcnc_source_cutter_comp_tool_offset_error.err"
 # Source basis: LinuxCNC src/emc/rs274ngc/interp_convert.cc
+# convert_control_mode(), convert_coordinate_system(), and convert_home()
+# reject control-mode changes, coordinate-system changes, and G28/G30 while
+# cutter radius compensation is active.
+cutter_comp_g_error_cases=(
+    "linuxcnc_cutter_comp_control_mode_error|Cannot change control mode with cutter radius compensation on"
+    "linuxcnc_cutter_comp_coordinate_system_error|Cannot change coordinate systems with cutter radius compensation on"
+    "linuxcnc_cutter_comp_home_error|Cannot use g28 or g30 with cutter radius comp"
+)
+for case in "${cutter_comp_g_error_cases[@]}"; do
+    fixture=${case%%|*}
+    expected=${case#*|}
+    if CNC_SIM_RS274_FILE_MODE=1 CNC_SIM_RS274_VAR="$var_file" \
+        "$build_dir/linuxcnc_rs274_source_dump" "tests/gcode/$fixture.ngc" \
+        >"$output_dir/cnc_sim_linuxcnc_source_$fixture.json" 2>"$output_dir/cnc_sim_linuxcnc_source_$fixture.err"; then
+        echo "expected $fixture.ngc to fail" >&2
+        exit 1
+    fi
+    grep -Fq "$expected" "$output_dir/cnc_sim_linuxcnc_source_$fixture.err"
+done
+# Source basis: LinuxCNC src/emc/rs274ngc/interp_convert.cc
 # convert_m() rejects M63-M65/M67-M68/M48-M53 while cutter radius
 # compensation is active before enqueueing digital/analog output or override
 # canon side effects.