增加当前位置参数fixture验证

结论：新增 position_params fixture，覆盖 Z 轴运动与 #5420/#5421/#5422 当前坐标参数同步；最小 harness 输出当前位置参数，runtime 在直线运动后刷新相对位置参数。检查：git diff --check 通过；wasm-port/tests/native/verify_native_probes.sh 通过。

wasm-port/docs/porting-steps-standalone.md

@@ -360,6 +360,11 @@ Current verified progress:
   temporary wrapper behavior is based on LinuxCNC
   `interp_convert.cc::convert_distance_mode()` and
   `interp_convert.cc::convert_straight()`.
+- `tests/fixtures/gcode/position_params.ngc` and
+  `tests/fixtures/canon/position_params.events` cover Z-axis motion plus
+  current-position parameter visibility for `#5420`, `#5421`, and `#5422`.
+  The parameter source basis is LinuxCNC
+  `interp_parameter_def.hh` and `interp_namedparams.cc`.
 - This proves the current extracted interpreter slice can parse and execute a
   simple traverse and feed move through a standalone canonical event sink.
 
@@ -662,7 +667,7 @@ traverse path:
 
 1. replace the temporary minimal `convert_g()` implementation with thin
    wrappers around more vendored interpreter conversion code,
-2. add fixture coverage for `Z` moves and multi-axis current-position
+2. add a negative fixture for `G1` without feed rate to start pinning error
-   parameter updates,
+   semantics,
 3. keep all source changes inside `wasm-port/` and leave `../linuxcnc/`
    read-only.

wasm-port/runtime/core/linuxcnc_wrap/linuxcnc_interp_minimal_harness.cpp

@@ -101,6 +101,9 @@ int main(int argc, char **argv)
     std::cout << "setup.current_x=" << interp._setup.current_x << "\n";
     std::cout << "setup.current_y=" << interp._setup.current_y << "\n";
     std::cout << "setup.current_z=" << interp._setup.current_z << "\n";
+    std::cout << "setup.parameter_5420=" << interp._setup.parameters[5420] << "\n";
+    std::cout << "setup.parameter_5421=" << interp._setup.parameters[5421] << "\n";
+    std::cout << "setup.parameter_5422=" << interp._setup.parameters[5422] << "\n";
     std::cout << "setup.feed_rate=" << interp._setup.feed_rate << "\n";
     std::cout << "close_and_downcase=" << downcase_rc << "\n";
     std::cout << "normalized_line=" << line << "\n";

wasm-port/runtime/core/linuxcnc_wrap/linuxcnc_interp_minimal_runtime.cpp

@@ -349,6 +349,24 @@ bool Interp::is_pycallable(setup_pointer, const char *, const char *) { return f
 bool Interp::is_user_defined_g_code(int) { return false; }
 bool Interp::is_any_m_code_remapped(block_pointer, setup_pointer) { return false; }
 int Interp::convert_m(block_pointer, setup_pointer) { return INTERP_OK; }
+
+namespace {
+
+void update_relative_position_parameters(setup_pointer settings)
+{
+    settings->parameters[5420] = settings->current_x;
+    settings->parameters[5421] = settings->current_y;
+    settings->parameters[5422] = settings->current_z;
+    settings->parameters[5423] = settings->AA_current;
+    settings->parameters[5424] = settings->BB_current;
+    settings->parameters[5425] = settings->CC_current;
+    settings->parameters[5426] = settings->u_current;
+    settings->parameters[5427] = settings->v_current;
+    settings->parameters[5428] = settings->w_current;
+}
+
+}  // namespace
+
 int Interp::convert_g(block_pointer block, setup_pointer settings)
 {
     const int distance_mode = block->g_modes[GM_DISTANCE_MODE];
@@ -376,6 +394,7 @@ int Interp::convert_g(block_pointer block, setup_pointer settings)
         settings->current_z = incremental ? settings->current_z + block->z_number
                                           : block->z_number;
     }
+    update_relative_position_parameters(settings);
 
     if (block->motion_to_be == G_0) {
         settings->motion_mode = G_0;

wasm-port/tests/fixtures/canon/position_params.events

@@ -0,0 +1,9 @@
+canon_event=STRAIGHT_TRAVERSE line=1 x=1 y=2 z=3 a=0 b=0 c=0 u=0 v=0 w=0
+canon_event=SET_FEED_RATE rate=80
+canon_event=STRAIGHT_FEED line=2 x=1.5 y=1 z=5 a=0 b=0 c=0 u=0 v=0 w=0
+setup.current_x=1.5
+setup.current_y=1
+setup.current_z=5
+setup.parameter_5420=1.5
+setup.parameter_5421=1
+setup.parameter_5422=5

wasm-port/tests/fixtures/gcode/position_params.ngc

@@ -0,0 +1,2 @@
+G90 G0 X1.0 Y2.0 Z3.0
+G91 G1 X0.5 Y-1.0 Z2.0 F80.0