⚡ perf(layershell): Optimize std::string parameter passing by reference

[CipherCereal]

💡 What:
Updated CLayerShellProtocol::onGetLayerSurface (both declaration in LayerShell.hpp and definition in LayerShell.cpp) to accept namespace_ as a const std::string& instead of passing it by value (std::string).

🎯 Why:
Passing a std::string by value forces a heap allocation if the string length exceeds the small string optimization buffer (SSO). By passing a const reference, we eliminate this heap allocation when the function is invoked, saving unnecessary CPU and memory overhead during layer surface allocation.

📊 Measured Improvement:
While a formal microbenchmark could not be cleanly measured within the sandboxed environment due to system dependencies (aquamarine), this is a standard, fundamental C++ optimization. Avoiding deep copies on object construction is universally faster (reducing allocation overhead from O(N) to O(1)) and provides an incremental baseline performance gain that accumulates over many Wayland interactions. No regressions or functional changes are introduced as namespace_ is used strictly as a read-only parameter here before passing into object constructors.

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PR created automatically by Jules for task 17257361909917465648 started by @CosmicDorito-25

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