Integrate CA-CFAR detector: replace fixed-threshold comparator with adaptive sliding-window CFAR engine (22/22 regression PASS)

- Add cfar_ca.v: CA/GO/SO-CFAR with BRAM magnitude buffer, host-configurable
  guard cells, training cells, alpha multiplier, and mode selection
- Replace old threshold detector block in radar_system_top.v with cfar_ca
  instantiation; backward-compatible (cfar_enable defaults to 0)
- Add 5 new host registers: guard (0x21), train (0x22), alpha (0x23),
  mode (0x24), enable (0x25)
- Expose doppler_frame_done_out from radar_receiver_final for CFAR frame sync
- Add tb_cfar_ca.v standalone testbench (14 tests, 24 checks)
- Add Group 14 E2E tests: 13 checks covering range-mode (0x20) and all
  CFAR config registers (0x21-0x25) through full USB command path
- Update run_regression.sh with CFAR in lint, Phase 1, and integration compiles

9_Firmware/9_2_FPGA/run_regression.sh

@@ -73,6 +73,7 @@ PROD_RTL=(
     edge_detector.v
     radar_mode_controller.v
     rx_gain_control.v
+    cfar_ca.v
 )
 
 # Source-only RTL (not instantiated at top level, but should still be lint-clean)
@@ -376,6 +377,10 @@ 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 "CFAR CA Detector" \
+    tb/tb_cfar_ca.vvp \
+    tb/tb_cfar_ca.v cfar_ca.v
+
 echo ""
 
 # ===========================================================================
@@ -426,7 +431,7 @@ 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
+        rx_gain_control.v cfar_ca.v
 
     # E2E integration (46 strict checks: TX, RX, USB R/W, CDC, safety, reset)
     run_test "System E2E (tb_system_e2e)" \
@@ -440,7 +445,7 @@ if [[ "$QUICK" -eq 0 ]]; then
         matched_filter_multi_segment.v matched_filter_processing_chain.v \
         range_bin_decimator.v doppler_processor.v xfft_32.v fft_engine.v \
         usb_data_interface.v edge_detector.v radar_mode_controller.v \
-        rx_gain_control.v
+        rx_gain_control.v cfar_ca.v
 else
     echo "  (skipped receiver golden + system top + E2E — use without --quick)"
     SKIP=$((SKIP + 4))