formula: Neargye/magic_enum

[MeteorsLiu]

Summary:

• Add the Neargye/magic_enum LLAR Formula with source-proven v0.9.2 and v0.9.7 thresholds.
• Publish relocatable magic_enum.pc metadata and verify the Conan consumer through pkg-config.

Validation:

• llar test --verbose ./Neargye/magic_enum@v0.9.2 --os darwin --arch arm64
• llar test --verbose ./Neargye/magic_enum@v0.9.6 --os darwin --arch arm64
• llar test --verbose ./Neargye/magic_enum@v0.9.7 --os darwin --arch arm64
• llar test --verbose ./Neargye/magic_enum@v0.9.8 --os darwin --arch arm64
• Repeated v0.9.7 cache-hit onTest; v0.8.1/v0.9.1 reject below the supported formula floor.

Closes #302

[fennoai]

The v0.9.7 formula and relocatable pkg-config consumer path are consistent with the upstream install contract. One compatibility issue remains in the older threshold: v0.9.4–v0.9.6 need the Conan recipe's header-layout normalization before they can share the v0.9.2 formula.

[fennoai]

[P1] Preserve the nested headers for v0.9.4–v0.9.6

This threshold also selects v0.9.4, v0.9.5, and v0.9.6, but those upstream tags changed their source layout to include/magic_enum/*.hpp. Their CMake install rules flatten that directory into include/*.hpp; the Conan recipe explicitly copies the installed headers back into include/magic_enum for exactly these versions. As written, consumers using the documented/newer interface #include <magic_enum/magic_enum.hpp> fail for every 0.9.4–0.9.6 package even though the formula's own test only exercises the legacy top-level include. Add the same compatibility copy for this version interval, or introduce a separate threshold/formula that preserves the nested layout.