Session artifact pills - Show references as a separate item in the response body/footer, instead of as an artifact pill

**Current**: References are showing up as artifact pills on top of prompt box. This goes against the principle of pills - "session generated artifacts", and pollutes the most important actionable pills.

**[Needs deisgn]**
Idea 1: Just visually elevate the importance of references in the response body itself (websites referenced, files referenced etc.)
Idea 2: Bring back the "used references" concept that sits at a response level (perhaps move it in footer).