Merge upstream dev through 5846fa19

Import Airoha GPS RTC backup sleep, 24 contact search results, and the T-Echo Lite USB companion target. Preserve existing GPS telemetry and power-saving controls, crypto alignment checks, ESP32 RTC recovery, and RAK11310 dynamic-preference compatibility.

Validate GPS sleep acknowledgments with their NMEA checksum and add six native regression tests covering retry, drain, corruption, grace timeout, and timer rollover.

Verified: 1648 native and KISS modem tests; targeted nRF52, companion routing, one-key DM, and clock checks; T1000-E BLE, MeshTracker X1 USB, and T-Echo Lite USB companion builds.

src/Utils.h

@@ -50,7 +50,7 @@ public:
 
   /**
    * \brief  checks the MAC (in leading bytes of 'src'), then if valid, decrypts remaining bytes in src.
-   * \returns  zero if MAC is invalid, otherwise the length of decrypted bytes in 'dest'
+   * \returns  zero if MAC is invalid or ciphertext is not block-aligned, otherwise the length of decrypted bytes in 'dest'
   */
   static int MACThenDecrypt(const uint8_t* shared_secret, uint8_t* dest, const uint8_t* src, int src_len);
 

src/helpers/BaseChatMesh.h

@@ -16,7 +16,7 @@ static_assert(MAX_CORRELATED_CLI_TEXT_LEN <= MAX_TEXT_LEN,
 
 #include "ContactInfo.h"
 
-#define MAX_SEARCH_RESULTS   8
+#define MAX_SEARCH_RESULTS   24
 
 #define MSG_SEND_FAILED       0
 #define MSG_SEND_SENT_FLOOD   1

src/helpers/sensors/AirohaSleep.h

@@ -0,0 +1,24 @@
+#pragma once
+#include <helpers/sensors/LocationProvider.h>
+#ifdef GPS_NMEA_DEBUG
+#include <helpers/UsbLogging.h>
+#endif
+
+// Board must keep the GPS RTC backup pin powered and can cut GPS power once we return.
+// Returns true if the command was acked within 3 attempts, otherwise returns false.
+static inline bool airohaEnterSleep(LocationProvider* nmea) {
+  for (uint8_t attempt = 0; attempt < 3; attempt++) {
+    nmea->drain();
+    nmea->sendSentence("$PAIR650,0");
+    if (nmea->waitFor("$PAIR001,650,0", 50)) {  // wait for the command received signal
+      #ifdef GPS_NMEA_DEBUG
+      if (mesh::isUsbLoggingEnabled()) {
+        mesh::usbLoggingPort().printf("Airoha RTC Backup sleep command accepted by GPS after %u attempts\r\n", attempt + 1);
+      }
+      #endif
+      nmea->waitFor("$PAIR650,0", 50); // give the GPS 50ms grace to signal it is ready for sleep
+      return true;
+    }
+  }
+  return false;
+}

src/helpers/sensors/LocationProvider.h

@@ -73,6 +73,8 @@ public:
     virtual bool isValid() = 0;
     virtual long getTimestamp() = 0;
     virtual void sendSentence(const char * sentence);
+    virtual bool waitFor(const char* prefix, uint32_t timeout_ms) { return false; }
+    virtual void drain() { }
     virtual void reset() = 0;
     virtual void begin() = 0;
     virtual void stop() = 0;

src/helpers/sensors/MicroNMEALocationProvider.h

@@ -198,10 +198,34 @@ public :
         return timestamp <= 0x7FFFFFFFUL ? static_cast<long>(timestamp) : 0;
     } 
 
+    void drain() override { while (_gps_serial->available()) _gps_serial->read(); }
+
+    const char* getSentence() const { return nmea.getSentence(); }
+
     void sendSentence(const char *sentence) override {
         nmea.sendSentence(*_gps_serial, sentence);
     }
 
+    bool waitFor(const char* prefix, uint32_t timeout_ms) override {
+        size_t plen = strlen(prefix);
+        uint32_t timeout = millis() + timeout_ms;
+        while ((int32_t)(millis() - timeout) < 0) {
+            if (_gps_serial->available()) {
+                char c = _gps_serial->read();
+                #ifdef GPS_NMEA_DEBUG
+                if (mesh::isUsbLoggingEnabled()) mesh::usbLoggingPort().print(c);
+                #endif
+                // MicroNMEA also returns true for a complete sentence with a
+                // bad checksum. A damaged ACK must not confirm GPS sleep.
+                if (nmea.process(c) && MicroNMEA::testChecksum(nmea.getSentence())
+                    && strncmp(nmea.getSentence(), prefix, plen) == 0) return true;
+            } else {
+                yield();
+            }
+        }
+        return false;
+    }
+
     void loop() override {
 
         size_t processed = 0;