docs: document the single universal (Vulkan) installer build

README.md

@@ -142,18 +142,28 @@ npm install
 npm run tauri dev      # CPU/NPU build
 ```
 
-**GPU (Vulkan) build.** whisper.cpp's GPU backends are compiled in (not downloaded at runtime),
-so a GPU build needs a one-time toolchain setup — the **Vulkan SDK**, a **Ninja** generator, and
-a short target dir (to dodge Windows' 260-char path limit in the shader build):
+**Release build (single universal installer).** whisper.cpp's GPU backends are compiled in (not
+downloaded at runtime), so the release build needs a one-time toolchain setup — the **Vulkan SDK**,
+a **Ninja** generator, and a short target dir (to dodge Windows' 260-char path limit in the shader
+build):
 
 ```bash
 # after: Vulkan SDK installed, ninja.exe on PATH, vcvars64 loaded
 set VULKAN_SDK=C:\VulkanSDK\1.4.350.0
 set CMAKE_GENERATOR=Ninja
 set CARGO_TARGET_DIR=C:\wt
-npm run tauri build -- --features vulkan
+npm run tauri build -- --features vulkan --config src-tauri/tauri.vulkan.conf.json
 ```
 
+This one build covers **every** machine: Vulkan accelerates all GPUs (NVIDIA/AMD/Intel), the Intel
+NPU path works via the runtime OpenVINO download, and CPU is the fallback. The `--features vulkan`
+binary links `vulkan-1.dll`, so `build.rs` stages the redistributable Vulkan **loader** (from
+`VULKAN_SDK\Bin`, or System32) next to the exe and `tauri.vulkan.conf.json` bundles it into the
+installer — the app then launches even on a machine with no GPU driver (it reports zero Vulkan
+devices and decodes on the CPU). DirectML is intentionally not offered here because Vulkan already
+covers those GPUs; it's the GPU path only in the plain `npm run tauri build` (no Vulkan) variant,
+kept as an internal fallback.
+
 CUDA (NVIDIA-only, faster) is planned as an optional variant. The full, gotcha-annotated build
 recipe lives in the project notes.