SDK support for `spark.user`
Surface `user` in SDK to template (#45) Towards https://github.com/github/spark/issues/104 Relies on https://github.com/github/workbench-sdk/pull/275 and should be merged + prebuilt as soon as possible after. * Adds necessary proxying for vite to get us working in dev * Moves to import from the new shared spark file instead of llm to get the window setup (which also imports the LLM bits...)