Native Stratum mining server with tiered routing and GPU miner tool

[Boblepointu]

Summary

Adds a built-in Stratum v1 mining server to doged, eliminating the need for external pool software. The server plugs directly into the node's block assembly and validation pipeline, using Scrypt PoW throughout — no SHA-256 mining path.

Stratum server (src/stratum/)

• Full Stratum v1 protocol: mining.subscribe, mining.authorize, mining.notify, mining.submit
• Job manager that builds work from CreateNewBlock, splits the coinbase for extranonce injection, and computes merkle branches
• Share validation against Scrypt PoW hash with configurable difficulty and optional variable difficulty (vardiff)
• Merge-mining support via createauxblock / submitauxblock RPCs, respecting Dogecoin's AuxPoW chain ID (0x62) and fabe6d6d prefix
• Libevent-based TCP server with thread-safe bufferevent handling for cross-thread broadcast
• Worker session management with idle timeout and per-worker stats
• JSON stats endpoint at /stratum/status

Tiered routing (stratumrouter + stratumproxy)

• Prioritized work sourcing: local node (when synced) → upstream pool proxy → failover between healthy pools → warning on solo fallback
• Upstream pool connector with health monitoring, automatic reconnection, and extranonce relay
• Fully transparent to downstream miners — tier switches trigger clean job broadcasts
• Configurable via -stratumproxy=host:port:user[:pass[:priority]], -stratumpreferlocal, -stratumwarnsolo

Miner tool (tools/miner/)

• Standalone Scrypt(1024,1,1) Stratum miner with OpenCL GPU and CPU fallback
• OpenCL kernel implementing PBKDF2-SHA256 → Salsa20/8 ROMix → target check
• Zero external dependencies (self-contained JSON parser, Scrypt implementation)
• Auto-detects GPU devices and adjusts work size to fit VRAM
• doged-miner -o stratum+tcp://host:port -u worker -p x [--gpu 0] [--cpu 4]

Integration

• Stratum server lifecycle wired into init.cpp (start after chainstate load, interrupt/stop on shutdown)
• BCLog::STRATUM logging category for dedicated debug output
• createauxblock and submitauxblock RPCs added to rpc/mining.cpp
• CMake wiring for all new modules and test suites

Testing

• 10 Boost unit test suites covering protocol parsing, config validation, worker state, job creation, share validation, auxpow, stats, proxy, and router logic
• 5 Python functional tests for subscribe/authorize flow, share submission, auxpow, vardiff retarget, and tier routing
• Verified end-to-end on regtest: miner connects, receives jobs, finds Scrypt shares, blocks accepted on-chain