⚡ Bolt: Memoize chat messages and thoughts to prevent O(N^2) re-renders

[teerthsharma]

💡 What: Extracted ChatMessage and ThoughtItem out of ChatInterface and wrapped them in React.memo().

🎯 Why: During text streaming and message accumulation, the state array triggers full-list re-renders on every streamed chunk. Since each message/thought renders individually without knowing if it's identical to the last render, we see an O(N^2) rendering bottleneck in React components mapped out of state arrays.

📊 Impact: Massively reduces CPU overhead during message streaming. Only the newly added message/thought, or the currently updating streamed message, will re-render, reducing re-renders from O(N^2) to near O(1) per update.

🔬 Measurement: Can be verified by using React DevTools Profiler and observing component rendering times when new chunks are streamed in via the DSP bus, or by sending a long stream of data to the kernel.

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PR created automatically by Jules for task 12859738300327082868 started by @teerthsharma

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