Feat: Collections

- Include collection name in catalog
- Push to named collection
- Define a collection setting, populated by querying R2R on initialization, annotated with the number of documents
- Use it for RAG query

- Legacy: move current contents from Default to cired-hal

Start by locating the R2R initialization, catalog handling, collection-setting code, and RAG query entry point. Trace how the current Default collection is selected, then verify that named collections are listed with document counts, receive pushed documents, are used for RAG queries, and that the legacy contents move to cired-hal.

Written by the indexing model from the issue text.