Add Sqlite with sqlite-vec as an alternative for Codebase Indexing

[adaptive-shield-matrix]

Problem

The official Wiki only describes/recommends qdrant (cloud + self hosted) + gemini for vector databases.
https://docs.roocode.com/features/codebase-indexing

I think SQLite should be an option as well, because it makes Roo code less reliant on external services and has much lower memory consumption than running the services locally in a docker container.

Performance comparsion

Here is a video comparing vector databases
https://www.youtube.com/watch?v=X0PwwfcGSHU
Benchmark code
https://github.com/andrisgauracs/Vector-DB-Benchmark-for-Music-Semantic-Search

I added SQLite (with some PRAGMA performance options) and
I'm getting even better throughput than all the dedicated vector databases.
andrisgauracs/Vector-DB-Benchmark-for-Music-Semantic-Search#1

My bechmark code with sqlite included
https://github.com/adaptive-shield-matrix/Vector-DB-Benchmark-for-Music-Semantic-Search

Embedding model

The all-MiniLM-L6-v2 seems like a good choice for code as well,
since code is (nearly) always exclusively in english and requires about 400 mb of memory to run.
https://huggingface.co/sentence-transformers/all-MiniLM-L6-v2

[NaccOll]

What you need is already there, but you have to wait

#7076
#6471