Rebrand hush3 to DragonX and share RandomX dataset across mining threads

Minimal rebrand (see compliant-rebrand branch for full rebrand):
- Rename binaries: hushd/hush-cli/hush-tx → dragonxd/dragonx-cli/dragonx-tx
- Default to DRAGONX chain params without -ac_* flags (randomx, blocktime=36, private=1)
- Update configure.ac: AC_INIT([DragonX],[1.0.0])
- Update client version string and user-agent to /DragonX:1.0.0/
- Add chainparams.cpp with DRAGONX network parameters
- Update build.sh, miner.cpp, pow.cpp for DragonX
- Add bootstrap-dragonx.sh utility script
- Update .gitignore for release directory

Share single RandomX dataset across all mining threads:
- Add RandomXDatasetManager with readers-writer lock, reducing RAM from
  ~2GB per thread to ~2GB total plus ~2MB per thread for the VM scratchpad
- Add LogProcessMemory() diagnostic helper for Linux and Windows

src/pow.cpp

@@ -339,6 +339,7 @@ unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHead
     memset(zflags,0,sizeof(zflags));
     if ( pindexLast != 0 )
         height = (int32_t)pindexLast->GetHeight() + 1;
+
     if ( ASSETCHAINS_ADAPTIVEPOW > 0 && pindexFirst != 0 && pblock != 0 && height >= (int32_t)(sizeof(ct)/sizeof(*ct)) )
     {
         tipdiff = (pblock->nTime - pindexFirst->nTime);
@@ -685,7 +686,10 @@ bool CheckEquihashSolution(const CBlockHeader *pblock, const CChainParams& param
     return true;
 }
 
-// Static objects for CheckRandomXSolution
+int GetRandomXInterval() { return GetArg("-ac_randomx_interval", 1024); }
+int GetRandomXBlockLag() { return GetArg("-ac_randomx_lag", 64); }
+
+// Cached RandomX validation state — reused across calls, protected by mutex
 static std::mutex cs_randomx_validator;
 static randomx_cache *s_rxCache = nullptr;
 static randomx_vm *s_rxVM = nullptr;
@@ -862,6 +866,7 @@ bool CheckProofOfWork(const CBlockHeader &blkHeader, uint8_t *pubkey33, int32_t
         if ( HUSH_LOADINGBLOCKS != 0 )
             return true;
 
+        /*
         if ( SMART_CHAIN_SYMBOL[0] != 0 || height > 792000 )
         {
             if ( Params().NetworkIDString() != "regtest" )
@@ -881,6 +886,7 @@ bool CheckProofOfWork(const CBlockHeader &blkHeader, uint8_t *pubkey33, int32_t
             }
             return false;
         }
+        */
     }
     /*for (i=31; i>=0; i--)
      fprintf(stderr,"%02x",((uint8_t *)&hash)[i]);