⚡ Bolt: [performance improvement] Optimize intermediate vector allocation during string collection in casing formatting

[cloudesize67-cmd]

💡 What: Replaced .collect::<Vec<_>>().join("") with .collect::<String>() in xdk-lib/src/casing.rs when generating PascalCase strings. Added comment explaining optimization.

🎯 Why: The original implementation mapped over an iterator, collected all resulting strings into an intermediate Vec<String>, and then iterated over them again to join them into a final single string. This created redundant allocations and memory overhead. Using .collect::<String>() skips the intermediate Vec entirely and collects the string fragments directly into a single result string.

📊 Impact: Minor memory savings and execution speedup within the string casing formatter. No longer allocates a Vec for every PascalCase string conversion operation.

🔬 Measurement: Verified with cargo test -p xdk-lib, running all 110 casing tests, as well as executing make check to verify standard formatter compliance.

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PR created automatically by Jules for task 8304024276824596896 started by @cloudesize67-cmd

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