Fix CommonJS runtime compatibility

[zth]

What changed

• normalize the DataLoader constructor through a CommonJS compatibility helper
• provide true CommonJS stable-stringify and Relay connection helpers
• make compiler-generated CJS and ESM runtimes reference the compatible helpers
• exercise DataLoader loads, connection/base64 helpers, CommonJS dependency paths, and packed artifacts
• run package/release tests on Node 20.11.0
• prepare the 1.3.4 patch release

Root cause

The CommonJS DataLoader binding compiled to require("dataloader").default, although dataloader 2.x exports its constructor directly. The generated CommonJS runtime also synchronously required local .mjs helpers, which is unsupported on the lower end of ResGraph’s declared Node range.

Validation

• npm run build
• npm run test:package
• opam exec -- make test