docs(rfc): add RFC 0037 deterministic simulation harness

[azimafroozeh]

What & why

This PR adds RFC 0037: the deterministic simulation harness, the real engine in a fully controlled world where one (scenario, seed) pair names one exact execution.

• Design first (five components: reach, fault injection, oracle, volume, method), then the determinism contract with what holds and what remains, reference-level detail, and the invariants walk.
• Engages the two prior positions directly: RFC-016's tooling survey gains the row it lacked (a custom-seam harness on stock tokio), and RFC-032's normalized replay is treated as a boundary choice, with this contract stronger where it matters (IDs and timestamps seed-determined rather than normalized away).
• test(bench): add node-vs-edge logical cost v0 #503 is addressed element by element in a disposition table, with its techniques credited and its real-backend role proposed for absorption into the harness's v2, gated on a same-ruler reconciliation of the two instruments' numbers.
• The benchmarking use implements the counting side of RFC-031.
• Measured results cited: 12 findings across 8,000+ universes, four public issues (bug: branch merge with a net-zero delta fails permanently with "table version already exists" #473, bug: apply_schema breaks traversal queries on open handles until the store is reopened #494, bug: after a failed init, cleanup deletes a completed store's schema files but not its data, leaving it unable to open or re-init #495, bug: operations racing branch_delete fail with an unclassified "Not found" branch-ref error #515), crash-state enumeration 326/326 with zero violations, and the per-operation cost golden.

Backing issue / RFC

• Is an RFC PR: docs/rfcs/0037-deterministic-simulation-harness.md

Local verification

• Docs-only PR, one markdown file added; no build, test, or CI-gate commands apply, so none were run.

Greptile Summary

RFC 0037 proposes a deterministic simulation harness that runs the real engine under controlled storage, time, randomness, scheduling, workloads, and fault injection.

• Defines reach, fault injection, oracle, volume, and accounting components.
• Specifies deterministic replay, crash-state enumeration, concurrent-universe boundaries, and reference-level seams.
• Describes coverage, benchmarking, provenance, invariants, alternatives, and follow-up work.

Confidence Score: 5/5

The documentation-only PR appears safe to merge.

No blocking failure remains.

Important Files Changed

Filename	Overview
docs/rfcs/0037-deterministic-simulation-harness.md	Adds the proposed architecture, determinism contract, reference design, measured boundaries, and adoption considerations for a deterministic engine simulation harness.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart LR
  Pair["Scenario + seed"] --> Sampler["Seeded sampler"]
  Sampler --> World["Controlled universe"]
  Faults["Fault and crash plans"] --> World
  World --> Engine["Real Omnigraph engine"]
  Engine --> Store["In-memory object store"]
  Engine --> Observations["Observation channels"]
  Model["Independent reference model"] --> Oracles["Oracles and detectors"]
  Observations --> Oracles
  Oracles --> Verdict["Deterministic verdict"]
  World --> Ledger["Run record and coverage ledger"]
  Verdict --> Ledger

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