TrueGrip Alpha

Add TrueGrip Skyrim VR SKSE plugin

Adds TrueGrip, an SKSE VR plugin to persistently adjust equipped-hand position/rotation for two-handed weapons. Implements HIGGS integration (higgsinterface001, HiggsInternals), calibration controller (GripCalibrationController), persistent store (GripStore using JSON), weapon tracking/geometry, transform math, input sink, haptic feedback, settings, and plugin entry (main.cpp). Also includes xmake build files, default config (Assets/config/TrueGrip.ini), README and .gitignore. Features logging, atomic save, diagnostics, and initial support for HIGGS-aware calibration and rendering adjustments.