feat(js): auto-resolve TypeScript extensions for relative imports

[akapug]

Summary

When a TypeScript file imports a relative path without an extension (e.g., import { x } from './helper'), Elide now tries resolving with TypeScript extensions before falling back to the default module resolution.

Problem

Currently, multi-file TypeScript projects don't work in Elide because relative imports like ./helper fail to resolve - Elide doesn't try ./helper.ts.

Reproduction:

// main.ts
import { helper } from './helper'
console.log(helper())

// helper.ts
export function helper(): string {
  return 'Hello from helper'
}

Running elide main.ts fails with TypeError: Module not found: './helper'

Solution

Added TypeScript extension resolution in ElideUniversalJsModuleLoader:

1. When resolving a relative import from a TypeScript source
2. And the specifier has no extension
3. Try extensions in order: .ts, .tsx, .mts, .cts, .js, .mjs, .cjs, .jsx
4. Also try index file resolution (./foo → ./foo/index.ts)

This matches the behavior of tsc and other TypeScript tooling.

Note

For production apps, bundling with esbuild is still recommended. This enhancement improves DX for simple multi-file scripts.