Add real-world benchmark fixtures

[longlho]

Summary

• add pinned VS Code, Grafana, and Kibana benchmark fixtures via MODULE.bazel
• replace the synthetic benchmark generator with a Benchmark.js harness over those fixtures
• document the motivation, Knip comparison, contribution workflow, and README benchmark results
• parallelize Codescythe parsing with Rayon and compact JSON output for benchmark runs

Validation

• git diff --check
• cargo fmt --all --check
• bazel test //...
• node --experimental-transform-types benchmarks/run.ts --help
• smoke benchmarks for vscode, grafana, and kibana with --samples 1 --warmups 0