Benchmarks

Doc	What it measures
jit.md	JIT compile + run latency on macOS ARM64
polyglot-compilers.md	`in compile` vs installed native compilers on polyglot samples
self-host-vs-native.md	`in build` vs rustc (time, binary size, startup) on `in-cli`

Regenerate:

./scripts/bench-self-host.sh && python3 scripts/render-self-host-bench-md.py
./scripts/bench_polyglot_compilers.v   # polyglot matrix

Swift-vs-in benchmark removed; use polyglot-compilers for cross-language compile-time comparison.