build(deps-dev): drop tsx in favor of type stripping

[dsanders11]

Lets drop tsx, we can make do without it.

[claude]

LGTM — simple, mechanical dev-tooling change.

What was reviewed: the package.json script changes (tsx replaced with node --experimental-strip-types), the five benchmark .ts files' import extension change from ./generate-fixtures.js to ./generate-fixtures.ts (required since Node's type-stripping loader resolves .ts directly), and the yarn.lock diff — confirmed it only removes tsx and its transitive deps (esbuild platform packages, get-tsconfig, resolve-pkg-maps) with no other changes. Also checked the engines field (node >=22.12.0), which supports --experimental-strip-types.

Extended reasoning...

Dev-tooling-only change: benchmark scripts and package.json/yarn.lock, no library or runtime code paths touched, no security-sensitive surface. Change is small, self-contained, and mechanical (swap tsx for Node's native type-stripping flag plus matching import extension updates), with the lockfile diff confirmed to only drop tsx and its transitive dependencies.