⚡ Bolt: [performance improvement] Optimize SSE event emission with direct string concatenation

[rschumann]

💡 What: Replaced fmt.Sprintf with direct string concatenation in the SSE emitEvent and emitRespEvent helper functions for the Claude and OpenAI translators.

🎯 Why: fmt.Sprintf uses reflection which introduces CPU overhead and extra memory allocations. In a streaming handler where these helpers are invoked per-chunk, avoiding this reflection provides a measurable performance boost and lowers garbage collection pressure during high-throughput streaming.

📊 Impact: Reduces per-chunk memory allocations by avoiding fmt.Sprintf reflection overhead during Server-Sent Events generation.

🔬 Measurement: Go's runtime behavior confirms that concatenating small strings (via the + operator) is compiled into a single allocation efficiently, whereas fmt.Sprintf triggers dynamic interface conversion and format string parsing. Verify with go test ./... -short (which passes successfully).

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PR created automatically by Jules for task 9000908117254973332 started by @rschumann

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