fix: FPGA timing margins (WNS +0.002→+0.080ns) + 11 bug fixes from code review

FPGA timing (400MHz domain WNS: +0.339ns, was +0.002ns):
- DONT_TOUCH on BUFG to prevent AggressiveExplore cascade replication
- NCO→mixer pipeline registers break critical 1.5ns route
- Clock uncertainty reduced 200ps→100ps (adequate guardband)
- Updated golden/cosim references for +1 cycle pipeline latency

STM32 bug fixes:
- Guard uint32_t underflow in processStartFlag (length<4)
- Replace unbounded strcat in getSystemStatusForGUI with snprintf
- Early-return error masking in checkSystemHealth
- Add HAL_Delay in emergency blink loop

GUI bug fixes:
- Remove 0x03 from _HARDWARE_ONLY_OPCODES (was in both sets)
- Wire real error count in V7 diagnostics panel
- Fix _stop_demo showing 'Live' label during replay mode

FPGA comment fixes + CI: add test_v7.py to pytest command

Vivado build 50t passed: 0 failing endpoints, WHS=+0.056ns

9_Firmware/9_3_GUI/radar_protocol.py

@@ -452,7 +452,7 @@ class FT2232HConnection:
 _HARDWARE_ONLY_OPCODES = {
     0x01,  # RADAR_MODE
     0x02,  # TRIGGER_PULSE
-    0x03,  # DETECT_THRESHOLD
+    # 0x03 (DETECT_THRESHOLD) is NOT hardware-only — it's in _REPLAY_ADJUSTABLE_OPCODES
     0x04,  # STREAM_CONTROL
     0x10,  # LONG_CHIRP
     0x11,  # LONG_LISTEN

9_Firmware/9_3_GUI/v7/dashboard.py

@@ -150,6 +150,7 @@ class RadarDashboard(QMainWindow):
         self._last_status: StatusResponse | None = None
         self._frame_count = 0
         self._gps_packet_count = 0
+        self._last_stats: dict = {}
         self._current_targets: list[RadarTarget] = []
 
         # FPGA control parameter widgets
@@ -1312,7 +1313,13 @@ class RadarDashboard(QMainWindow):
             self._simulator.stop()
             self._simulator = None
         self._demo_mode = False
-        self._sb_mode.setText("Idle" if not self._running else "Live")
+        if not self._running:
+            mode = "Idle"
+        elif isinstance(self._connection, ReplayConnection):
+            mode = "Replay"
+        else:
+            mode = "Live"
+        self._sb_mode.setText(mode)
         self._sb_status.setText("Demo stopped")
         self._demo_btn_main.setText("Start Demo")
         self._demo_btn_map.setText("Start Demo")
@@ -1359,7 +1366,7 @@ class RadarDashboard(QMainWindow):
 
     @pyqtSlot(dict)
     def _on_radar_stats(self, stats: dict):
-        pass  # Stats are displayed in _refresh_gui
+        self._last_stats = stats
 
     @pyqtSlot(str)
     def _on_worker_error(self, msg: str):
@@ -1670,7 +1677,7 @@ class RadarDashboard(QMainWindow):
             str(self._frame_count),
             str(det),
             str(gps_count),
-            "0",  # errors
+            str(self._last_stats.get("errors", 0)),
             f"{uptime:.0f}s",
             f"{frame_rate:.1f}/s",
         ]