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.

packaging/d4r.ini

@@ -21,6 +21,10 @@ ShowWatermark = false
 FrameAge = 0
 
 [Kernels]
+; Prioritize fidelity over speed. Uses accuracy variants of all native kernels, preserves NVIDIA's
+; intermediate FP8/f16 rounding and denormal handling, and keeps NGX's synchronization calls.
+; Slower but aims to match RTX DLSS.
+PreferAccuracy = false
 ; Hand-written RDNA3 and RDNA4 kernels for the DLSS 4 and 4.5 networks (d4r\kernels). Each one is used
 ; only when your DLSS library's code for that kernel matches the code it was written for; otherwise
 ; that kernel is compiled from NVIDIA's code instead, which is slower but still correct.