chore(prototype): move legacy python miner into prototype folder with usage docs

prototype/config.py.example

@@ -0,0 +1,67 @@
+"""Complete miner configuration example.
+
+This file documents all options supported by the program.
+"""
+
+import multiprocessing as mp
+
+# ---------------------------------------------------------------------------
+# RPC (Bitcoin Core)
+# ---------------------------------------------------------------------------
+RPC_USER = "user"
+RPC_PASSWORD = "password"
+RPC_HOST = "127.0.0.1"
+RPC_PORT = 18443
+
+# ---------------------------------------------------------------------------
+# Wallet
+# ---------------------------------------------------------------------------
+# Address that receives the coinbase reward.
+# It must be valid for the node you are connected to.
+WALLET_ADDRESS = ""
+
+# ---------------------------------------------------------------------------
+# Mining
+# ---------------------------------------------------------------------------
+# Network behavior:
+# - regtest:     0 -> use network target; >0 -> max_target / factor; <0 -> forced to 0.1
+# - non-regtest: ignored and always set to 1.0
+DIFFICULTY_FACTOR = 1.0
+
+# Supported values:
+# - "incremental": initial nonce is 0, then increments
+# - "random":      initial nonce is random, then increments by batch
+# - "mixed":       initial nonce is random, then increments
+NONCE_MODE = "incremental"
+
+# Interval (seconds) to update the header timestamp.
+# 0 disables periodic timestamp updates.
+TIMESTAMP_UPDATE_INTERVAL = 30
+
+# Number of nonces computed per batch (int > 0 recommended).
+BATCH = 10_000
+
+# Custom message inserted into coinbase scriptSig.
+COINBASE_MESSAGE = "/py-miner/"
+
+# Extranonce values used in coinbase scriptSig.
+# Must be hexadecimal strings (only 0-9a-fA-F) with even length.
+EXTRANONCE1 = "1234567890abcdef"
+EXTRANONCE2 = "12341234"
+
+# Practical note: total coinbase scriptSig must remain <= 100 bytes.
+
+# ---------------------------------------------------------------------------
+# Worker
+# ---------------------------------------------------------------------------
+# Same semantics as config.py:
+# - >0: use that exact number of processes
+# - <=0: use all available CPU cores
+_NUM_PROCESSORS = 0
+NUM_PROCESSORS = _NUM_PROCESSORS if _NUM_PROCESSORS > 0 else mp.cpu_count()
+
+# ---------------------------------------------------------------------------
+# Watchdog
+# ---------------------------------------------------------------------------
+# Best-block polling interval (seconds).
+CHECK_INTERVAL = 20