fix(replication): widen local storage admission range

[mickvandijke]

Summary

• add a storage-admission width helper for close group size plus margin 2
• use the widened local admission range for client PUT, fresh chunk replication, chunk repair hint admission, and stored-record pruning retention
• keep audit targets, prune proof checks, paid-list K checks, quorum targets, and fresh outgoing close-group selection on strict close-group sizing
• update prune e2e candidate selection so prunable records are outside the widened storage-admission range

SemVer

• patch: widens local storage-admission tolerance without changing public APIs or network message formats

Tests

• cargo fmt --all -- --check
• cargo clippy --all-targets --all-features -- -D warnings
• cargo test --lib --features test-utils -- --nocapture
• cargo test --lib --features test-utils replication::pruning -- --nocapture
• cargo test --test e2e --features test-utils replication::test_fresh_replication_propagates_to_close_group -- --nocapture
• cargo test --test e2e --features test-utils replication::test_prune_pass_requires_remote_confirmation_before_delete -- --nocapture
• cargo test --test e2e --features test-utils replication::prune_deletes_at_proof_threshold_and_retains_below_it -- --nocapture