feat: add HIL diagnostics and meter health handling

src/lora_transport.cpp

@@ -1,4 +1,5 @@
 #include "lora_transport.h"
+#include "hil_trace.h"
 #include <LoRa.h>
 #include <SPI.h>
 #include <math.h>
@@ -13,6 +14,7 @@ static void note_reject(RxRejectReason reason) {
     if (now_ms - g_last_rx_reject_log_ms >= 1000) {
       g_last_rx_reject_log_ms = now_ms;
       Serial.printf("lora_rx: reject reason=%s\n", rx_reject_reason_text(reason));
+      hil_trace_eventf("lora_reject", "\"reason\":\"%s\"", rx_reject_reason_text(reason));
     }
   }
 }
@@ -84,6 +86,13 @@ bool lora_send(const LoraPacket &pkt) {
   buffer[idx++] = static_cast<uint8_t>(crc >> 8);
   buffer[idx++] = static_cast<uint8_t>(crc & 0xFF);
 
+  if (pkt.payload_type == PayloadType::MeterBatch && hil_fault_take(HilFault::CorruptChunk) && idx > 7) {
+    // Flip a payload byte after calculating the frame CRC so the receiver's
+    // production CRC path rejects this one HIL frame.
+    buffer[5 + (pkt.payload_len > 6 ? 6 : 0)] ^= 0x01;
+    hil_trace_event("fault_injected", "\"fault\":\"corrupt_chunk\"");
+  }
+
   LoRa.beginPacket();
   if (SERIAL_DEBUG_MODE) {
     t2 = millis();