fix: align deep benchmarks with runtime contracts

[smiggleworth]

Summary

• update Tier 3 Lease routes and Notice fanout bursts to match production route depth and lane capacity
• keep Tier 4 Stream reads within the wire response budget and preserve retryable error messages
• replace obsolete oversized payload rows with the maximum valid Stream event contract
• update the benchmark documentation for the legal maximum event size

Why

The full hosted benchmark run after #229 made Tier 1 and Tier 2 green, then exposed stale Tier 3 and Tier 4 fixtures that no longer matched the production Lease, Notice, and Stream wire contracts.

Validation

• cargo fmt --all -- --check
• cargo test --workspace
• cargo clippy --locked --workspace --all-targets --all-features -- -D warnings -D clippy::pedantic
• cntryl-tools validate-benchmarks
• cargo bench --bench tier3* --features benchkit --quiet
• all Tier 4 benchmark binaries, including a complete tier4_stream_shapes run