Include attempt-1 devcontainer Dockerfile (AI+human)

.devcontainer/Dockerfile

@@ -0,0 +1,42 @@
+# ClaudeOS build environment
+#
+# Provides everything needed to build and test a bare-metal i386 kernel:
+#   - Clang + LLD for cross-compilation to i386-elf
+#   - GRUB 2 tools for generating bootable ISO and floppy images
+#   - QEMU (i386) for running integration tests
+#   - CMake + Ninja for the build system
+#   - xorriso and mtools used internally by grub-mkrescue / grub-mkimage
+
+FROM --platform=linux/amd64 alpine:3.23
+
+RUN apk add --no-cache \
+    # Core build tools
+    clang \
+    lld \
+    cmake \
+    ninja \
+    make \
+    git \
+    # GRUB image generation
+    grub \
+    grub-bios \
+    xorriso \
+    mtools \
+    # QEMU for running the OS
+    qemu-system-i386 \
+    # Handy utilities
+    file \
+    ca-certificates
+
+# Verify the cross-compilation toolchain can produce an i386-elf binary.
+# Compile and link separately so ld.lld is invoked directly, avoiding the
+# host gcc linker driver (which rejects -m32 on non-x86 hosts such as aarch64).
+RUN echo 'void _start(void){for(;;)__asm__("hlt");}' > /tmp/test.c \
+    && clang -v -target i386-elf -march=i386 -ffreestanding -fno-stack-protector \
+             -c /tmp/test.c -o /tmp/test.o \
+    && ld.lld -m elf_i386 -e _start --nostdlib /tmp/test.o -o /tmp/test.elf \
+    && file /tmp/test.elf | grep -q "ELF 32-bit.*386" \
+    && echo "Toolchain OK" \
+    && rm /tmp/test.c /tmp/test.o /tmp/test.elf
+
+WORKDIR /workspaces/claude-os