Provide shared Bun 1.4.3 in Node.js and Bun modules

[Kodylow]

Why

Make Bun’s built-in TypeScript checker available through the shared toolchain, without a project-local Bun package.

What changed

• Pin the official Bun 1.4.3 Linux x64 release with a fixed source checksum, using the existing Nixpkgs packaging.
• Share that package between Node.js tool modules and the standalone bun-1.4 module.
• Extend the upgrade map from bun-1.3 to bun-1.4; older Bun IDs follow the existing chain.

Test plan

Passed: Nix formatting; active-module evaluation; older/newer Bun alias equality; pinned Bun package build; bun --version reports 1.4.3 and bun check --help succeeds. Selected nodejs-24 and bun-1.4 module builds and evaluation of every module passed. Generated module metadata resolves Bun 1.4.3 on PATH for both.

Rollout

Publish the module bundle before consumers require bun check. Node.js versions stay unchanged; existing Bun IDs upgrade to 1.4.3. Consumers should feature-detect the checker during rollout. Revert the pin and upgrade-map entry to roll back.

• This is fully backward and forward compatible

~ written by ⠕ Replit