fix(extension-sdk): use posix path to support windows build

[Cassolette]

Description

Extensions built using the sdk on Windows will not work out of the box. This is because the entrypoint path is being exported with non-POSIX compliant file separators.

{
  "entrypoint": "js\\remoteEntry-Cx_RoXqY.mjs"
}

Export posix‑compatible paths to Vite to fix issues on Windows.

Related Issue

• Fixes <issue_link>

How Has This Been Tested?

• Manual: checked correct entrypoint path in manifest.json build output

{
  "entrypoint": "js/remoteEntry-Cx_RoXqY.mjs"
}

Types of changes

• Bugfix
• Enhancement (a change that doesn't break existing code or deployments)
• Breaking change (a modification that affects current functionality)
• Technical debt (addressing code that needs refactoring or improvements)
• Tests (adding or improving tests)
• Documentation (updates or additions to documentation)
• Maintenance (like dependency updates or tooling adjustments)

[Cassolette]

Ref:

vite/packages/vite/src/node/build.ts

      entryFileNames: ssr
        ? `[name].${jsExt}`
        : libOptions
          ? ({ name }) =>
              resolveLibFilename(
                libOptions,
                format,
                name,
                root,
                jsExt,
                packageCache,
              )
          : path.posix.join(options.assetsDir, `[name]-[hash].${jsExt}`),
      chunkFileNames: libOptions
        ? `[name]-[hash].${jsExt}`
        : path.posix.join(options.assetsDir, `[name]-[hash].${jsExt}`),

[Cassolette]

If we're already hardcoding path separators it might be worth it to just stick to that 🙂

[JammingBen]

LGTM, thanks!