test(network): prototype GetBlocks regulation properties

[evan-forbes]

Motivation

Exercise the peer-message addition contract on one concrete request. GetBlocks needs property checks for its wire bounds, invalid ranges, canonical encoding, and specification-defined Work charge.

Solution

• Add one production GetBlocks declaration for payload, allocation, range, and Work bounds.
• Enforce the message-specific payload cap from the fixed frame header before payload allocation.
• Reject GetBlocks ranges that extend above Height::MAX.
• Add reusable legal-value, deterministic-boundary, bounded-payload, frame, and canonical-encoding checks.
• Define a closed inventory of single-rule violations and execute every violation deterministically.
• Compare the declared Work calculation with an independent transcription of the specification equation.

This draft does not claim full regulation conformance. The production Work bucket, Delay, concurrency slots, and terminal refunds remain follow-up work.

Testing

• cargo test -p zakura-network block_sync::property_tests -- --nocapture
• cargo test -p zakura-network zakura::transport::registry::tests -- --nocapture
• cargo test -p zakura-network codec_ -- --nocapture
• cargo test -p zakura-network inbound_frame_cap_rejects_over_message_frame_before_reading_payload -- --nocapture
• cargo clippy -p zakura-network --lib --tests --no-deps -- -D warnings
• cargo fmt --all -- --check
• codespell on the changed design and specification documents

Changelog

Added the explicit internal-only fragment at docs/changelog/unreleased/860.md.

Specifications & References

Built on the peer message regulation design and specification in #747.

Follow-up Work

Implement the production serving Work bucket, Delay, concurrency-slot ownership, terminal refunds, and the stateful two-peer comparison.