[friendly-ripper]

Part 8 of 10 · base refactor/07-documentation · 7 commits

The xmake build carries recipes, locks, and vendored package trees that duplicate what a pinned Zig build can hold in one graph. This PR moves the mod, the platform entry points, the macOS launcher, the tests, and release packaging to Zig 0.16, then removes the xmake setup it replaces.

What changes

• The core mod builds with Zig: dependency URLs and pins are fixed for Zig 0.16, SDK downloads are verified, and target settings are shared. The IL2CPP, Unity, SPUD, protobuf, logging, and settings sources build as C++23. macOS uses the SDK curl and Windows uses Schannel, so no OpenSSL build is added.
• The Swift launcher, librsync bridge, and app resources build with Zig. Native archives are repacked with Apple libtool for Swift linking, ARM64 and Intel outputs merge into universal binaries, updates extract with the system tar instead of the PLzma dependency, and Windows DLL provenance is verified before packaging.
• The TOML parser builds once as a compiled library instead of being instantiated in every consumer, and settings and shortcut headers use forward declarations so parser internals stay private. Abseil is limited to the protobuf-lite source closure.
• Compile time is cut where the old build repeated work. Logging and HTTP sources compile together. Protobuf generation selects only the sync entry points and their transitive field types. Generated image headers use escaped string chunks instead of millions of byte initializers.
• Swift compiles as one module independently of native archive linkage. Recursive JSON key ordering moves into one translation unit, and macOS release features compile four to a unit.
• CI builds release artifacts and Debug fixtures in the same Zig graph. The xmake targets, recipes, locks, and formatting helpers that Zig replaced are removed, and the build docs cover platform commands, output paths, SDK provisioning, packaging, and contributor checks.

Testing

Every commit passes zig build test-il2cpp test-mod test-sync on Zig 0.16, cross-builds the Windows mods with -Dtarget=x86_64-windows-msvc, and builds the macOS mods with -Dtarget=aarch64-macos.14.6. Nothing was run in the game.