test(bench): add node-vs-edge logical cost v0

[aaltshuler]

Summary

• add one selectively imported benchmark-v0 module for the node-versus-edge insert comparator, record schema, correctness oracle, ceilings, identity stamps, and S3 cleanup
• extend the existing shared cost counters with manifest writes and aggregate logical-operation totals
• run fresh indexed fixtures in AB/BA order on local storage and RustFS, requiring correctness, non-vacuous evidence, repeatability, and per-field upper ceilings
• add a required local PR context and a post-merge/tag/manual RustFS qualifier, each retaining JSONL plus the full log for 14 days
• document the current benchmark machinery, runnable commands, RFC-031 gaps, and CI/branch-protection policy

Calibrated v0 contract

Backend	Node insert	Edge insert
Local filesystem	14 ops (12 reads, 2 writes)	34 ops (32 reads, 2 writes)
RustFS 1.0.0-beta.12	37 ops (30 reads, 7 writes)	57 ops (50 reads, 7 writes)

Both backends reproduced exactly across AB/BA order. RustFS reproduced across independent runs and left no keys under either dedicated test prefix.

These are logical calls observed by Lance data-table and __manifest object-store wrappers. They do not claim physical HTTP attempts, SDK retries, non-Lance control-object I/O, bytes, billing, timing, or RSS.

Validation

• cargo fmt --all --check
• actionlint .github/workflows/ci.yml
• shellcheck scripts/*.sh
• cargo clippy --workspace --all-targets --locked -- -D warnings -W clippy::dbg_macro
• cargo clippy --workspace --all-targets --locked --features omnigraph-engine/failpoints,omnigraph-cluster/failpoints -- -D warnings -W clippy::dbg_macro
• RUST_MIN_STACK=16777216 cargo test --workspace --locked --features omnigraph-engine/failpoints,omnigraph-cluster/failpoints
• full write_cost target: 13 passed
• exact local comparator, including failpoints build and JSONL validation
• exact configured RustFS comparator against the workflow-pinned image/digest
• benchmark_scenario_contract plus warm-read, merge, and branch-control cost suites
• scripts/check-agents-md.sh and git diff --check

Scope boundary

This is the minimal current-build v0 gate for one node insert versus one edge insert. It does not implement the RFC-031 previous-release-versus-candidate lifecycle matrix, physical counting proxy, timing/RSS/byte collection, reporter, baselines, waivers, release manifests, or evidence bundles.

The declarative branch-protection context is included in this PR. Applying it to live main protection remains a post-merge maintainer action.