fix: make generated TypeScript ESM tests cross-platform - #919

Tested locally on Node 24 (Windows).

Moving FASTIFY_AUTOLOAD_TYPESCRIPT=1 and ts-node/esm registration into register-ts-esm.mjs loaded via --import cleanly resolves the Windows cmd.exe syntax issue and removes the loader deprecation warning.

One small cross-platform fix is needed in test/generate-typescript-esm.test.js:

On Windows, the walker yields backslash paths like \package.json, so line 116's filter does not match:

const copiedFileCount = Object.keys(expected).filter(file => file !== '/package.json').length

Because '\package.json' !== '/package.json' evaluates to true, \package.json is included in copiedFileCount, raising the expected assertions to 42 while only 41 run (verifyCopy skips package.json):

✖ should finish successfully with typescript template (1708.2601ms)
  'plan expected 42 assertions but received 41'

Normalizing separators or checking !file.endsWith('package.json') fixes it:

const copiedFileCount = Object.keys(expected).filter(file => !file.endsWith('package.json')).length

With that adjustment, all 6 tests in test/generate-typescript-esm.test.js pass cleanly on Windows.

Thanks for testing on Windows, @SameRainbows. Good catch. Fixed in d7f3270 by normalizing path separators before the comparison (file.replace(/\\/g, '/') !== '/package.json') rather than endsWith, so only the root package.json is excluded.

I also rebased onto the latest main. npm test passes locally (unit:cli-js: 229 passed, 3 skipped).