chore: copy tables from current mcp

[paoloricciuti]

I've copied the tables from the current mcp (cc @khromov ) and ported them to drizzle+sqlite.

I've also added an embeddings field in both content and distilled_content and since it's nullable modified the distance function to make sure it can handle NULL embeddings values.

I'm not sure if we should stick to this structure/general workflow or if we want to do something different. The one issue I see with this is that the db needs to be constantly updated with the new content of the docs which is probably fine but I wonder if we can do better...maybe serve the chunked content from svelte.dev and just fetch the right thing? That wouldn't work with the distilled version but I wonder if that's enough of a boost to justify the need for a sync job etc.

That would also prevent the usage of embeddings unless we generate them on svelte.dev when deploying. And obviously that would also prevent the usage offline unless we come up with some wanky plan to switch to a db only locally when offline.

Regardless, just opening this up to start moving the weel.