[Suggestion] Add a per-turn usage timeline #35

Is your feature request related to a problem? Please describe.
Session totals make it difficult to identify which turn caused a cost spike, context jump, slow response, or excessive tool usage.

Describe the solution you'd like
Add a chronological /analyze view showing each turn's model, cost, input/cache/reasoning/output tokens, duration, tool calls, and status, with expandable details.

Additional context
Execution order: 3, after #34. Reuse the persistent turn telemetry and existing scroll/export patterns.