Integrate MTI canceller and DC notch filter for ground clutter removal

MTI canceller (2-pulse, H(z)=1-z^{-1}) between range decimator and
Doppler processor. Subtracts previous chirp from current, nulling DC
Doppler (stationary clutter). Pass-through when host_mti_enable=0.

DC notch filter (post-Doppler, pre-CFAR) zeros bins within
+/-host_dc_notch_width of DC. Complements MTI for residual clutter.

New host registers: 0x26 (mti_enable), 0x27 (dc_notch_width).
Both default to 0 (disabled) - fully backward-compatible.

Verification: 23/23 regression, 29/29 MTI standalone, 3/3 real-data
co-sim (5137/5137 exact match) all PASS.

9_Firmware/9_2_FPGA/run_regression.sh

@@ -74,6 +74,7 @@ PROD_RTL=(
     radar_mode_controller.v
     rx_gain_control.v
     cfar_ca.v
+    mti_canceller.v
 )
 
 # Source-only RTL (not instantiated at top level, but should still be lint-clean)
@@ -377,6 +378,10 @@ run_test "RX Gain Control (digital gain)" \
     tb/tb_rx_gain_control.vvp \
     tb/tb_rx_gain_control.v rx_gain_control.v
 
+run_test "MTI Canceller (ground clutter)" \
+    tb/tb_mti_canceller.vvp \
+    tb/tb_mti_canceller.v mti_canceller.v
+
 run_test "CFAR CA Detector" \
     tb/tb_cfar_ca.vvp \
     tb/tb_cfar_ca.v cfar_ca.v
@@ -405,7 +410,7 @@ if [[ "$QUICK" -eq 0 ]]; then
         chirp_memory_loader_param.v latency_buffer.v \
         matched_filter_multi_segment.v matched_filter_processing_chain.v \
         range_bin_decimator.v doppler_processor.v xfft_32.v fft_engine.v \
-        rx_gain_control.v
+        rx_gain_control.v mti_canceller.v
 
     # Golden compare
     run_test "Receiver (golden compare)" \
@@ -417,7 +422,7 @@ if [[ "$QUICK" -eq 0 ]]; then
         chirp_memory_loader_param.v latency_buffer.v \
         matched_filter_multi_segment.v matched_filter_processing_chain.v \
         range_bin_decimator.v doppler_processor.v xfft_32.v fft_engine.v \
-        rx_gain_control.v
+        rx_gain_control.v mti_canceller.v
 
     # Full system top (monitoring-only, legacy)
     run_test "System Top (radar_system_tb)" \
@@ -431,7 +436,7 @@ if [[ "$QUICK" -eq 0 ]]; then
         matched_filter_multi_segment.v matched_filter_processing_chain.v \
         range_bin_decimator.v doppler_processor.v xfft_32.v fft_engine.v \
         usb_data_interface.v edge_detector.v radar_mode_controller.v \
-        rx_gain_control.v cfar_ca.v
+        rx_gain_control.v cfar_ca.v mti_canceller.v
 
     # E2E integration (46 strict checks: TX, RX, USB R/W, CDC, safety, reset)
     run_test "System E2E (tb_system_e2e)" \
@@ -445,7 +450,7 @@ if [[ "$QUICK" -eq 0 ]]; then
         matched_filter_multi_segment.v matched_filter_processing_chain.v \
         range_bin_decimator.v doppler_processor.v xfft_32.v fft_engine.v \
         usb_data_interface.v edge_detector.v radar_mode_controller.v \
-        rx_gain_control.v cfar_ca.v
+        rx_gain_control.v cfar_ca.v mti_canceller.v
 else
     echo "  (skipped receiver golden + system top + E2E — use without --quick)"
     SKIP=$((SKIP + 4))