Update testnet minimum chain work and default assume valid values to current state.
Restore security check in getblocktemplate RPC to prevent usage during initial block download.
- Change BIP34Height from 0 to 8192 to match mainnet activation
- Adjust nPowTargetTimespan from 1 day to 14 days for better difficulty stability
- Add nPowTargetSpacingV2 parameter for future compatibility
- Swap rule change activation threshold and miner confirmation window values
- Clarify fPowAllowMinDifficultyBlocks comment
The previous consensus parameters prevented the node from completing
initial sync without manually importing blocks. Updated chainparams so
a fresh node can fully synchronize on its own.
Update all references to 'testnet3' to 'testnet' for consistency. This includes:
- Changing magic bytes in network messages
- Updating directory paths and configuration files
- Modifying documentation and test framework references
- Adjusting chain parameters and validation logic
