Convert global std::string to constexpr const char*

[gaul]

Found via bugprone-throwing-static-initialization.

[Copilot]

Pull request overview

This PR removes non-trivially-initialized global/static std::string storage (flagged by bugprone-throwing-static-initialization) by switching to compile-time string literals (constexpr const char*) for fixed sysfs path lists.

Changes:

• Replaced std::vector<std::string> blocklist paths with a static constexpr const char*[] in the Intel platform check.
• Removed the cthd_cdev_backlight static std::string member declaration and replaced the implementation with a file-local static constexpr const char*[] device path list.
• Replaced a preprocessor macro (#define MAX_BACKLIGHT_DEV) with a static constexpr int.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/thd_platform_intel.cpp	Uses a constexpr string-literal array for platform blocklist paths, avoiding static std::string initialization.
src/thd_cdev_backlight.h	Removes the static std::string member declaration that required static initialization.
src/thd_cdev_backlight.cpp	Defines backlight device paths as a file-local constexpr array and replaces the macro with constexpr.

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