⚡ Bolt: Zero-allocation case-insensitive prefix matching

[callmeradical]

💡 What: Replaced strings.ToLower with strings.EqualFold for case-insensitive prefix matching on the content type header in cmd/sergeant-mcp-client/proxy.go.
🎯 Why: strings.ToLower forces a memory allocation when checking if a string starts with a specific prefix. In hot paths (like processing HTTP responses), this creates unnecessary GC pressure. strings.EqualFold achieves the same result with zero allocations.
📊 Impact: Eliminates a memory allocation per proxy response when checking for the text/event-stream content type, slightly reducing GC overhead.
🔬 Measurement: A Go micro-benchmark comparing strings.HasPrefix(strings.ToLower(s), prefix) vs len(s) >= len(prefix) && strings.EqualFold(s[:len(prefix)], prefix) would show 0 allocations for the latter.

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PR created automatically by Jules for task 929279684384335444 started by @callmeradical

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