Updates based on spec mode discussion

@rwjblue or I will try to update this later with details, but I'm starting this issue to capture the notes so we can iterate on it—

- relation of keywords/built-ins w/imports/etc.
- how various embeddings should work
- how whitespace handling should work
- how escaping (e.g. nested ``, or, notionally in the future, nested `` or nested `<query>` etc.) should work

Context: [spec notes from 2022/05/10](https://www.notion.so/emberteam/9a55c49297c34764839a9fecd8f3470e)

Start by reviewing the linked spec notes from 2022/05/10 and the four listed discussion areas: keywords and imports, embeddings, whitespace handling, and escaping. The issue does not identify files, tests, an entry point, or a defined completion condition, so the intended changes need to be clarified before implementation.

Written by the indexing model from the issue text.