Function classify_kind 

pub fn classify_kind(entries: &[TimelineEntry]) -> Kind

Classify a set of timeline entries into a canonical Kind.

Uses a lightweight keyword-scoring approach:

• Scans assistant messages (where classification signal is strongest)
• Scores plan vs report keywords
• Conversations win by default when neither plan nor report signal is strong

The approach is intentionally conservative: ambiguous content falls to Conversations (the most common kind), not Other.