devops : reduce Vulkan Docker image to 39.4% of its original size (now 692 MB) (#4038)

* devops : do not install recommended packages

Also:
- Replace apt-get with apt
- Explicitly install ca-certificates

* devops : remove development packages from runtime

* devops : copy only CLI executables and shared libraries

Won't copy compiled tests, source code and other build artifacts.

* devops : remove bash as entrypoint

With this change, arguments passed to `docker run` are forwarded
directly to the selected command.

Having `bash -c` in the entrypoint will cause additional arguments to be
interpreted according to shell command-string semantics, which makes
commands such as model downloaders and CLI tools behave unexpectedly
unless `--entrypoint` is specified explicitly or the whole command is
quoted.

Removing it restores the conventional Docker behavior of: `docker run
IMAGE COMMAND ARG...` passing `ARG` to `COMMAND` (not to `bash`).

* docs : fix + enhance Docker examples

.devops/main-vulkan.Dockerfile

@@ -1,20 +1,32 @@
 FROM ubuntu:24.04 AS build
 WORKDIR /app
 
-RUN apt-get update && \
-  apt-get install -y build-essential wget cmake git libvulkan-dev spirv-headers glslc \
+RUN apt update && \
+  apt install --no-install-recommends -y build-essential ca-certificates cmake git glslc libvulkan-dev spirv-headers wget \
   && rm -rf /var/lib/apt/lists/* /var/cache/apt/archives/*
 
 COPY .. .
 RUN --mount=type=secret,id=HF_TOKEN,required=false,env=HF_TOKEN make base.en CMAKE_ARGS="-DGGML_VULKAN=1"
+# Copy only CLI executables and shared libraries (not compiled tests, nor source code or other build artifacts)
+RUN mkdir -p /runtime/usr/local/bin /runtime/usr/local/lib && \
+    for path in build/bin/*; do \
+      name="${path##*/}"; \
+      case "$name" in \
+        *.so|*.so.*) cp -a "$path" /runtime/usr/local/lib/ ;; \
+        test-*|main|bench) ;; \
+        *) cp -a "$path" /runtime/usr/local/bin/ ;; \
+      esac; \
+    done
+
 
 FROM ubuntu:24.04 AS runtime
 WORKDIR /app
 
-RUN apt-get update && \
-  apt-get install -y curl ffmpeg libsdl2-dev wget cmake git libvulkan1 mesa-vulkan-drivers \
+RUN apt update && \
+  apt install --no-install-recommends -y \
+    ca-certificates curl ffmpeg libvulkan1 mesa-vulkan-drivers \
   && rm -rf /var/lib/apt/lists/* /var/cache/apt/archives/*
 
-COPY --from=build /app /app
-ENV PATH=/app/build/bin:$PATH
-ENTRYPOINT [ "bash", "-c" ]
+COPY --from=build /runtime/ /
+COPY --from=build /app/models/download-* /usr/local/bin/
+RUN ldconfig