⚡ Bolt: [performance improvement] optimize string allocations in Casing module

[cloudesize67-cmd]

💡 What:

• Replaced .collect::<Vec<_>>().join("") with .collect::<String>() for Casing::Pascal in xdk-lib/src/casing.rs.
• Replaced .to_lowercase().collect::<String>() with .to_lowercase().to_string() for character case conversion in camel_case.

🎯 Why:

• Joining string iterators by collecting them into an intermediate vector (Vec) first causes unnecessary heap allocations. Using .collect::<String>() on a String or &str iterator directly extends a single underlying String allocation.
• char::to_lowercase() returns an iterator (because some characters map to multiple characters when lowercased). Using .collect::<String>() creates standard iterator overhead, whereas leveraging its built-in Display implementation via .to_string() provides a more direct string generation path.

📊 Impact:

• Eliminates intermediate vector allocations during SDK casing operations (particularly PascalCase and camelCase conversions), slightly reducing memory pressure and improving execution speed during high-volume generation.

🔬 Measurement:

• make check and make test-generator continue to pass. The logic behaves identically but more efficiently.

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PR created automatically by Jules for task 6533965806049265086 started by @cloudesize67-cmd

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