Add tokens-per-second (TPS) display during streaming

Feature Request: Live Tokens Per Second (TPS) Display

Problem

Users have no visibility into streaming throughput during Claude Code sessions. Knowing TPS helps evaluate model performance and response quality.

Proposed Solution

Display real-time TPS counter in the terminal UI during streaming responses, similar to OpenCode's @williamcr01/opencode-tps plugin.

Requirements

• Live TPS counter during streaming
• 5-second rolling window calculation
• Show "-" when idle/no tokens
• Non-intrusive placement (e.g., bottom-right corner)

Reference Implementation

OpenCode plugin @williamcr01/opencode-tps hooks into internal streaming events to calculate real-time TPS:

• Tracks token deltas via message.part.delta events
• Uses rolling window for smoothing
• Registers UI slot for display

Why This Helps

• Performance visibility during long responses
• Model comparison benchmarking
• Detecting rate limiting or throttling