Define a decentralized Network Validator and worker scoring protocol

[flo2517]

Design the single validator role exposed by OpenInfra, inspired by Bittensor subnet validators: Network Validators independently challenge Workers, evaluate delivered service, and submit attributable weights/scores. Substrate block producers/finality nodes are called Chain Authorities, not a second economic validator type. An accepted ADR is required before adding the validator executable/component boundary.

Acceptance criteria:

• define Network Validator identity, registration, authorization, stake/reputation, selection, and lifecycle;
• specify randomized challenges for compute, storage, network/bandwidth, availability, and reliability;
• define signed Protobuf evidence envelopes, deadlines, nonces, replay resistance, and bounded retention;
• document collusion, Sybil, self-validation, bribery, withholding, false-report, and weight-copying threats;
• define multi-validator weight aggregation, confidence, disputes, and incentives;
• preserve integer-only deterministic on-chain aggregation and keep detailed evidence off-chain.

[flo2517]

Resolved by ADR-011 (accepted, merged in #40): docs/adr/011-network-validator-protocol.md defines Network Validator identity/registration/stake/lifecycle, randomized per-dimension challenges over the existing SolveChallenge RPC, signed bounded evidence envelopes, a threat table, and integer-only multi-validator aggregation with confidence/disputes/incentives. Implementation tracked in #29 (first slice landed in #43: pallet-network-validator).