feat: hybrid AGC (FPGA phases 1-3 + GUI phase 6) with timing fix

FPGA:
- rx_gain_control.v rewritten: per-frame peak/saturation tracking,
  auto-shift AGC with attack/decay/holdoff, signed gain -7 to +7
- New registers 0x28-0x2C (agc_enable/target/attack/decay/holdoff)
- status_words[4] carries AGC metrics (gain, peak, sat_count, enable)
- DIG_5 GPIO outputs saturation flag for STM32 outer loop
- Both USB interfaces (FT601 + FT2232H) updated with AGC status ports

Timing fix (WNS +0.001ns -> +0.045ns, 45x improvement):
- CIC max_fanout 4->16 on valid pipeline registers
- +200ps setup uncertainty on 400MHz domain
- ExtraNetDelay_high placement + AggressiveExplore routing

GUI:
- AGC opcodes + status parsing in radar_protocol.py
- AGC control groups in both tkinter and V7 PyQt dashboards
- 11 new AGC tests (103/103 GUI tests pass)

Cross-layer:
- AGC opcodes/defaults/status assertions added (29/29 pass)
- contract_parser.py: fixed comment stripping in concat parser

All tests green: 25 FPGA + 103 GUI + 29 cross-layer = 157 pass

9_Firmware/9_2_FPGA/radar_receiver_final.v

@@ -42,6 +42,13 @@ module radar_receiver_final (
     // [2:0]=shift amount: 0..7 bits. Default 0 = pass-through.
     input wire [3:0] host_gain_shift,
 
+    // AGC configuration (opcodes 0x28-0x2C, active only when agc_enable=1)
+    input wire        host_agc_enable,      // 0x28: 0=manual, 1=auto AGC
+    input wire [7:0]  host_agc_target,      // 0x29: target peak magnitude
+    input wire [3:0]  host_agc_attack,      // 0x2A: gain-down step on clipping
+    input wire [3:0]  host_agc_decay,       // 0x2B: gain-up step when weak
+    input wire [3:0]  host_agc_holdoff,     // 0x2C: frames before gain-up
+
     // STM32 toggle signals for mode 00 (STM32-driven) pass-through.
     // These are CDC-synchronized in radar_system_top.v / radar_transmitter.v
     // before reaching this module. In mode 00, the RX mode controller uses
@@ -60,7 +67,12 @@ module radar_receiver_final (
     // ADC raw data tap (clk_100m domain, post-DDC, for self-test / debug)
     output wire [15:0] dbg_adc_i,            // DDC output I (16-bit signed, 100 MHz)
     output wire [15:0] dbg_adc_q,            // DDC output Q (16-bit signed, 100 MHz)
-    output wire        dbg_adc_valid         // DDC output valid (100 MHz)
+    output wire        dbg_adc_valid,        // DDC output valid (100 MHz)
+
+    // AGC status outputs (for status readback / STM32 outer loop)
+    output wire [7:0]  agc_saturation_count, // Per-frame clipped sample count
+    output wire [7:0]  agc_peak_magnitude,   // Per-frame peak (upper 8 bits)
+    output wire [3:0]  agc_current_gain      // Effective gain_shift encoding
 );
 
 // ========== INTERNAL SIGNALS ==========
@@ -86,7 +98,9 @@ wire adc_valid_sync;
 // Gain-controlled signals (between DDC output and matched filter)
 wire signed [15:0] gc_i, gc_q;
 wire gc_valid;
-wire [7:0] gc_saturation_count;  // Diagnostic: clipped sample counter
+wire [7:0] gc_saturation_count;  // Diagnostic: per-frame clipped sample counter
+wire [7:0] gc_peak_magnitude;    // Diagnostic: per-frame peak magnitude
+wire [3:0] gc_current_gain;      // Diagnostic: effective gain_shift
 
 // Reference signals for the processing chain
 wire [15:0] long_chirp_real, long_chirp_imag;
@@ -160,7 +174,7 @@ wire clk_400m;
 // the buffered 400MHz DCO clock via adc_dco_bufg, avoiding duplicate
 // IBUFDS instantiations on the same LVDS clock pair.
 
-// 1. ADC + CDC + AGC
+// 1. ADC + CDC + Digital Gain
 
 // CMOS Output Interface (400MHz Domain)
 wire [7:0] adc_data_cmos;  // 8-bit ADC data (CMOS, from ad9484_interface_400m)
@@ -222,9 +236,10 @@ ddc_input_interface ddc_if (
     .data_sync_error()
 );
 
-// 2b. Digital Gain Control (Fix 3)
+// 2b. Digital Gain Control with AGC
 // Host-configurable power-of-2 shift between DDC output and matched filter.
-// Default gain_shift=0 → pass-through (no behavioral change from baseline).
+// Default gain_shift=0, agc_enable=0 → pass-through (no behavioral change).
+// When agc_enable=1: auto-adjusts gain per frame based on peak/saturation.
 rx_gain_control gain_ctrl (
     .clk(clk),
     .reset_n(reset_n),
@@ -232,10 +247,21 @@ rx_gain_control gain_ctrl (
     .data_q_in(adc_q_scaled),
     .valid_in(adc_valid_sync),
     .gain_shift(host_gain_shift),
+    // AGC configuration
+    .agc_enable(host_agc_enable),
+    .agc_target(host_agc_target),
+    .agc_attack(host_agc_attack),
+    .agc_decay(host_agc_decay),
+    .agc_holdoff(host_agc_holdoff),
+    // Frame boundary from Doppler processor
+    .frame_boundary(doppler_frame_done),
+    // Outputs
     .data_i_out(gc_i),
     .data_q_out(gc_q),
     .valid_out(gc_valid),
-    .saturation_count(gc_saturation_count)
+    .saturation_count(gc_saturation_count),
+    .peak_magnitude(gc_peak_magnitude),
+    .current_gain(gc_current_gain)
 );
 
 // 3. Dual Chirp Memory Loader
@@ -474,4 +500,9 @@ assign dbg_adc_i     = adc_i_scaled;
 assign dbg_adc_q     = adc_q_scaled;
 assign dbg_adc_valid = adc_valid_sync;
 
+// ========== AGC STATUS OUTPUTS ==========
+assign agc_saturation_count = gc_saturation_count;
+assign agc_peak_magnitude   = gc_peak_magnitude;
+assign agc_current_gain     = gc_current_gain;
+
 endmodule