fix: Keep @oclif/core external in editor server build

[Manrich121]

Problem

Running powersync edit config started the editor server, then returned a 500 on every request with:

Error: Cannot find module 'minimatch'
      Require stack:
      - .../cli-plugin-config-edit/editor-dist/server/_ssr/files.functions-*.mjs

Solution

Mark @oclif/core external for both the SSR pass (ssr.external) and the nitro pass (rollupConfig.external) so it is loaded from the published plugin's own node_modules, where minimatch resolves as an @oclif/core dependency.

AI Disclosure

I used Claude Code 5 Opus to debug this issue and implement the fix