[Good First Issue] Add automated Node.js and Bun CLI benchmark runner script

[pCwOrM]

Description

WERR features sub-2ms reflex decision routing in Python and browser JS environments. To make cross-runtime latency benchmarks easier for developers, we would love a lightweight CLI benchmark runner for Node.js and Bun.

Scope

• Create a script in benchmarks/node_benchmark.js that runs 1,000 synthetic state evaluations.
• Measure average latency, p50, p95, and p99.
• Output a clean ASCII summary table in the terminal.
• Ensure zero external npm dependencies (rely on standard performance.now()).

Acceptance Criteria

• Script runs cleanly with node benchmarks/node_benchmark.js
• Measures execution latency with standard high-resolution timer
• Strict air-gap: no network calls or external heavy packages