fix(security): Use `import.meta.hot` for communication with Vite 6.0.9+ (and 5.4.14+) dev server

[aklinker1]

Overview

WXT previously relied on connecting to Vite's dev server manually, instead of using import.meta.hot. Vite 6.0.9 introduced several changes that broke WXT's dev mode:

• Vite introduced a randomly generated auth token to ensure of your application can access it

  This broke WXT because WXT doesn't know what the token is. While it is possible to get the token from the dev server, it would take quite a bit of refactoring to route the token into the background script during development, so I'm not gonna do that. Instead, WXT now uses import.meta.hot.

  For MV2, WXT dynamically imports the vite/client package from the dev server. For MV3, we're updating dev mode to always set background.type: "module" in the manifest.

[!WARNING] This is technically a breaking change to dev mode, however, it should have no effect. WXT will continue to bundle the background as IIFE if you don't specify type: "module" in your entrypoint.

• CORS: TODO

Manual Testing

Install the new version from pkg.pr.new and spin up your extension in dev mode:

pnpm i https://pkg.pr.new/wxt@XXXX
pnpm dev

Related Issue

• This PR closes #1360
• This PR closes #1362

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[aklinker1]

Status update. I should have it all working, but for some reason I can't load the vite client from the server, debugging this.