[Copilot]

This PR adds the Phase 1 Crown successor scaffold on top of the Bitcoin Core v31.1 baseline: an isolated experimental Crown network plus the minimum validator configuration/runtime hooks needed for later BFT work. It keeps Bitcoin’s existing PoW block production and chain-selection behavior intact while introducing Crown-specific code under a narrow integration surface.

• Network isolation

  • adds ChainType::CROWN and wires it through chain selection, base params, chain params, CLI/help surfaces, Qt network styling, and functional-test message magic
  • introduces an experimental Crown network profile with dedicated datadir, ports, message magic, and distinct Bech32 HRP
  • keeps Crown-specific behavior out of existing Bitcoin networks

• Crown module boundary

  • adds src/crown/options.* and src/crown/validator.*
  • keeps validator definitions, quorum math, and runtime option handling inside src/crown/ rather than spreading Crown logic across upstream code

• Static validator scaffold

  • defines the four Phase 1 validators (validator-a through validator-d)
  • models only the data needed for future consensus work: validator id, consensus pubkey, and voting power
  • encodes exact quorum math for the fixed 25/25/25/25 voting-power split

• Validator runtime behavior

  • defaults Crown nodes to explicit non-validator operation
  • adds Crown validator startup options for enabling validator mode, selecting validator identity, and supplying a test-only private key
  • rejects validator configuration on non-Crown chains and validates dependent arguments cleanly

• ECC-safe initialization

  • defers private-key decoding, pubkey derivation, and identity matching until the post-ECC startup phase
  • retains only derived validator identity/runtime metadata after validation rather than keeping private keys in long-lived node state

• Tests and documentation

  • adds unit coverage for chain selection, validator math, key matching, option validation, and touched network-dependent cases
  • adds a functional startup test for Crown non-validator and validator flows
  • documents the Phase 1 patch surface, lifecycle constraints, and intentional regtest-like PoW/genesis posture

Example of the new Crown validator surface:

bitcoind -crown=1 \
  -crownvalidator=1 \
  -crownvalidatorid=validator-a \
  -crownvalidatorprivkey=0000000000000000000000000000000000000000000000000000000000000001