Add NJS-GROWTH-07 benchmark result data contract

[SebaSOFT]

Summary

Adds the NJS-GROWTH-07 benchmark/result-data contract for downstream proof assets without publishing or implying measured benchmark claims.

Deliverables

• docs/benchmarks/results.schema.json: machine-readable benchmark result schema with stable field names, units, and source explanations.
• benchmarks/sample-results.placeholder.json: deterministic placeholder fixture marked result_kind: placeholder_sample, is_placeholder: true, and claims_allowed: false.
• docs/benchmarks/methodology.md: competitor set, scenario matrix, input-size matrix, metric definitions, and placeholder-data policy.
• tests/contracts/benchmark-contract.test.ts: regression coverage for the schema, sample placeholder guardrails, competitor/scenario/input matrix, and VitePress discovery link.
• Adds docs navigation for proof assets and includes visual-proof/prompt-kit scaffolding for downstream visual agents.

Validation

• yarn lint ✅
• yarn test ✅ 11 files / 59 tests
• yarn build ✅
• yarn docs:build ✅
• yarn examples ✅

Guardrails

• No npm release.
• No fabricated benchmark results.
• Placeholder data is explicitly non-claim data and must not be used for public performance claims.

[gemini-code-assist]

Code Review

This pull request establishes the benchmark methodology, result schema, placeholder data, and visual proof guidelines for Neuron-JS, along with a contract test suite and necessary competitor dependencies. The review feedback correctly identifies that the results schema should require the result_kind field and suggests moving the schema file to the VitePress public directory so it can be served correctly, which cascades into updating reference paths across the documentation, READMEs, and tests.

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