Fix jina-code model alias

[Whamp]

codegraph embed --model jina-code currently points at a missing Hugging Face repo.

Current alias:

Xenova/jina-embeddings-v2-base-code

That repo returns 404. The published code model is:

jinaai/jina-embeddings-v2-base-code

Reproduction:

codegraph build .
codegraph embed --model jina-code

Actual result:

Could not locate file: "https://huggingface.co/Xenova/jina-embeddings-v2-base-code/resolve/main/config.json"

Expected result:

jina-code should load the published Jina code embedding model and build embeddings.

I also noticed the README says this model requires an HF token. Hugging Face reports jinaai/jina-embeddings-v2-base-code as public, so that note appears stale.