⚡ Bolt: [performance improvement] Avoid string allocations in native runtime value_to_string

[Tcode-Motion]

💡 What: Replaced format! and Vec::join allocations in value_to_string with a mutable &mut String buffer using std::fmt::Write.
🎯 Why: To improve performance by eliminating O(N) heap allocations and redundant copying when stringifying nested TsValue structures.
📊 Impact: Significantly reduces memory allocations and string copies during value conversions (like ts_say).
🔬 Measurement: Verify tests run faster or benchmark native value formatting.

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PR created automatically by Jules for task 3748299792517150468 started by @Tcode-Motion

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