fix: predict all CoQA turn answers instead of only the last turn

[rahulraj-jhawar-devrev]

Fixes #1231

Problem

CoQA implementation only predicts the last answer of each text. The official CoQA benchmark evaluates predictions for ALL turn_ids and averages results across turns.

Changes

• Modified CoQA utils to iterate over all turns instead of just the last one
• Maintains conversation context (previous Q&A pairs) for each turn prediction
• Output format matches official CoQA evaluation expectations

Implementation Details

• Added process_docs function that expands each conversation into multiple instances (one per turn)
• Each expanded instance contains the story and conversation history up to that specific turn
• The model predicts the answer for each turn with full context of previous Q&A pairs
• Version bumped to 4.0 to reflect the change in evaluation behavior

🤖 Generated with Claude Code

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