feat: sqlite-vector powered search

[jfolcini]

Before you file

• I searched open and closed issues and could not find a duplicate.
• I checked REVIEW-LATER.md and FEATURE-MAP.md for an existing entry.
• This proposal does not require introducing a new schema migration, op type, Zustand store, materializer queue, or sync message type — or, if it does, I am opening this issue specifically to discuss whether such a change is justified.

Problem

No semantis search

Proposed solution

Semantic search

Alternatives considered

https://github.com/sqliteai/sqlite-vector

Rough scope

L — 8 hours or more

User-facing surface

https://github.com/sqliteai/sqlite-vector

Anything else

No response