JP_STRICT: dynamic MAX_TEXT_LEN based on runtime CR value

Instead of compile-time LORA_CR define, MAX_TEXT_LEN is now determined
at runtime by reading the actual coding rate from the radio hardware.

Added getMaxTextLen() to RadioLibWrapper and Dispatcher:
- CR4/5: 48 bytes (~16 JP chars, TX ~3808ms)
- CR4/6: 32 bytes (~10 JP chars)
- CR4/7: 24 bytes (~8 JP chars)
- CR4/8: 16 bytes (~5 JP chars, default)

getCodingRate() added to CustomSX1262Wrapper to read codingRate
from RadioLib PhysicalLayer at runtime.

Tested: 48-byte limit with LORA_CR=5, 16-byte limit with LORA_CR=8.

src/Dispatcher.h

@@ -38,6 +38,10 @@ public:
 
   virtual float packetScore(float snr, int packet_len) = 0;
 
+#ifdef JP_STRICT
+  virtual int getMaxTextLen() const { return 1 * 16; }  // default: CR4/8
+#endif
+
   /**
    * \brief  starts the raw packet send. (no wait)
    * \param  bytes   the raw packet data

src/helpers/BaseChatMesh.cpp

@@ -395,8 +395,15 @@ void BaseChatMesh::onGroupDataRecv(mesh::Packet* packet, uint8_t type, const mes
 
 mesh::Packet* BaseChatMesh::composeMsgPacket(const ContactInfo& recipient, uint32_t timestamp, uint8_t attempt, const char *text, uint32_t& expected_ack) {
   int text_len = strlen(text);
+
+#ifdef JP_STRICT
+  int max_len = _radio->getMaxTextLen();
+  if (text_len > max_len) return NULL;
+  if (attempt > 3 && text_len > max_len - 2) return NULL;
+#else
   if (text_len > MAX_TEXT_LEN) return NULL;
   if (attempt > 3 && text_len > MAX_TEXT_LEN-2) return NULL;
+#endif
 
   uint8_t temp[5+MAX_TEXT_LEN+1];
   memcpy(temp, &timestamp, 4);   // mostly an extra blob to help make packet_hash unique

src/helpers/BaseChatMesh.h

@@ -5,26 +5,8 @@
 #include <helpers/AdvertDataHelpers.h>
 #include <helpers/TxtDataHelpers.h>
 
-// JP_STRICT: limit MAX_TEXT_LEN to keep TX time under 4s (ARIB STD-T108)
-// SF12/BW125, packet overhead ~44 bytes
-// CR4/5: 100 bytes total = ~3808ms → 56 bytes text → ~18 JP chars
-// CR4/6: 80 bytes total  = ~3530ms → 36 bytes text → ~12 JP chars
-// CR4/7: 70 bytes total  = ~3530ms → 26 bytes text →  ~8 JP chars
-// CR4/8: 60 bytes total  = ~3809ms → 16 bytes text →  ~5 JP chars
-#ifdef JP_STRICT
-  #if defined(LORA_CR) && (LORA_CR == 5)
-    #define MAX_TEXT_LEN  (3*CIPHER_BLOCK_SIZE)    // 48 bytes ~18 JP chars
-  #elif defined(LORA_CR) && (LORA_CR == 6)
-    #define MAX_TEXT_LEN  (2*CIPHER_BLOCK_SIZE)    // 32 bytes ~10 JP chars
-  #elif defined(LORA_CR) && (LORA_CR == 7)
-    #define MAX_TEXT_LEN  (1*CIPHER_BLOCK_SIZE+8)  // 24 bytes ~8 JP chars
-  #else
-    #define MAX_TEXT_LEN  (1*CIPHER_BLOCK_SIZE)    // 16 bytes ~5 JP chars
-  #endif
-#else
-  #define MAX_TEXT_LEN  (10*CIPHER_BLOCK_SIZE)  
+#define MAX_TEXT_LEN  (10*CIPHER_BLOCK_SIZE)  
 // must be LESS than (MAX_PACKET_PAYLOAD - 4 - CIPHER_MAC_SIZE - 1)
-#endif
 
 #include "ContactInfo.h"
 

src/helpers/radiolib/CustomSX1262Wrapper.h

@@ -36,4 +36,8 @@ public:
   bool getRxBoostedGainMode() const override {
     return ((CustomSX1262 *)_radio)->getRxBoostedGainMode();
   }
+
+  uint8_t getCodingRate() const override {
+    return ((CustomSX1262 *)_radio)->codingRate + 4;  // RadioLib stores 1-4, return 5-8
+  }
 };

src/helpers/radiolib/RadioLibWrappers.h

@@ -7,7 +7,7 @@ class RadioLibWrapper : public mesh::Radio {
 protected:
   PhysicalLayer* _radio;
   mesh::MainBoard* _board;
-  uint32_t n_recv, n_sent, n_recv_errors;
+  uint32_t n_recv, n_sent, n_recv_errors, _tx_start_ms;
   int16_t _noise_floor, _threshold;
   uint16_t _num_floor_samples;
   int32_t _floor_sample_sum;
@@ -38,8 +38,20 @@ public:
   }
 
   virtual float getCurrentRSSI() =0;
-  virtual int16_t performChannelScan();
+  virtual uint8_t getCodingRate() const = 0;
 
+#ifdef JP_STRICT
+  int getMaxTextLen() const {
+    uint8_t cr = getCodingRate();
+    if (cr <= 5) return 3 * 16;  // 48 bytes ~16 JP chars
+    if (cr == 6) return 2 * 16;  // 32 bytes ~10 JP chars
+    if (cr == 7) return 1 * 16 + 8; // 24 bytes ~8 JP chars
+    return 1 * 16;               // 16 bytes ~5 JP chars
+  }
+#endif
+
+  virtual int16_t performChannelScan();
+  
   int getNoiseFloor() const override { return _noise_floor; }
   void triggerNoiseFloorCalibrate(int threshold) override;
   void resetAGC() override;