fix: default distributions to automatic GPU support with CPU fallback

docs/SEMANTIC.md

@@ -33,6 +33,13 @@ an external OpenMP runtime. Production CMake supports cpu, auto, metal, vulkan,
 and cuda; CPU builds force GPU flags off. Runtime/provider parity and packaging
 on other operating systems remain independent release checks.
 
+The normal build/staging default is `auto`, shipping GPU support together with
+CPU fallback: Metal on macOS, Vulkan on Windows/Linux. Runtime detection chooses
+the usable device; users do not need hardware-specific builds. Release builders
+must have the relevant compilation SDK. Missing Vulkan/glslc now fails the
+normal build rather than silently omitting acceleration. Actual GPU parity,
+loader/dependency packaging and no-driver CPU fallback still require evidence.
+
 | Artifact | Bytes | SHA256 |
 | --- | ---: | --- |
 | embeddinggemma-2-Q8_0.gguf | 309,855,456 | 2188ac1deca4b77dffefd603c2776a9d76d9d74ec01841392982ebb840b09135 |
@@ -264,4 +271,4 @@ point-localization failures and unsuppressed no-answer results. Strong file
 recall is insufficient for accurate spoken-topic navigation. A ten-second audio
 experiment reduces some distances but does not close that gate; it is not a
 new default. Quality policies must be validated on held-out data rather than
-inventing thresholds from the evaluation corpus.
+inventing thresholds from the evaluation corpus.