Add accuracy mode and GLIBC 2.41 release builds

Add default-off PreferAccuracy with conservative native variants for every RDNA3/RDNA4 target and a separate JIT cache. Preserve fast defaults and reject mixed accuracy sets.

Add a pinned Debian build environment, rebuild all release components against GLIBC 2.41, and include toolchain provenance and release notes for the accuracy changes and the preceding artifact/synchronization fixes. Refs #6; CPU-overhead confirmation for #7 remains pending.

scripts/d4r_config.py

@@ -75,6 +75,7 @@ def main(argv):
         return
 
     env = {}
+    env["D4R_PREFER_ACCURACY"] = "1" if flag("Kernels", "PreferAccuracy") else "0"
 
     model = get("DLSS", "Model")
     if model is not None: