build: set up devcontainer and refactor kernel build

[robin-reckmann]

Add devcontainer support for kernel development with working clangd integration.

• Add separate macOS and Linux devcontainer configs for host-specific setup.
• Refactor kernel build setup to share builder image preparation and optionally build directly inside devcontainers.
• Remove repo clean-up step AFTER the kernel build to speed up the build, and keep changes in source tree for kernel development in the devcontainer.

[github-actions]

vamOS System Profile

Changes vs master

Metric	Change
Used space	3437.2MB → 3437.3MB (+.1MB)
Sparse image	3392.0MB → 3391.0MB (-1.0MB)
Package count	524 → 524

Directory size changes (>1MB)

Directory	Change

---

Metric	Value
Used space	3437.3MB / 5959.5MB
Files	56143
Directories	4762
Symlinks	3589
Packages	524

Top 10 Directories

Directory	Size

Category Breakdown

Category	Size	%
xbps packages	2502.8MB	72.8%
Python venv	591.7MB	17.2%
Firmware	11.2MB	.3%
Other	331.4MB	9.6%

Top 10 Packages by Size

Package	Size
mit-krb5-libs-1.21.3_1	270.4MB
gawk-5.3.2_1	210.3MB
llvm-21_3	148.6MB
libldns-1.9.2_1	124.3MB
pd-mapper-1.0_1	73.9MB
libclang21-21.1.7_1	70.2MB
glib-2.88.0_1	67.4MB
gcc-14.2.1+20250405_4	66.6MB
libcap-progs-2.78_1	56MB
cmake-4.2.2_2	53.2MB

Top 30 Files by Size

File	Size
/usr/lib/llvm/21/lib/libLLVM.so.21.1	124.3MB
/usr/lib/llvm/21/lib/libMLIR.so.21.1	89.7MB
/usr/lib/llvm/21/bin/mlir-transform-opt	82.9MB
/usr/lib/llvm/21/lib/libclang-cpp.so.21.1	56MB
/usr/lib/llvm/21/bin/mlir-translate	53.2MB
/usr/bin/uv	52.6MB
/usr/lib/llvm/21/bin/llvm-exegesis	52MB
/usr/lib/llvm/21/bin/llvm-bolt-binary-analysis	50.6MB
/usr/lib/gcc/aarch64-linux-gnu/14.2/gnat1	40.1MB
/usr/bin/gdb	39.1MB
/usr/lib/libgallium-26.1.3.so	37.7MB
/usr/lib/gcc/aarch64-linux-gnu/14.2/cc1plus	37.3MB
/usr/lib/libllvm-qcom.so	35.2MB
/usr/lib/gcc/aarch64-linux-gnu/14.2/cc1	35.2MB
/usr/lib/libRusticlOpenCL.so.1.0.0	34.3MB
/usr/lib/gcc/aarch64-linux-gnu/14.2/lto1	33.9MB
/usr/bin/lto-dump	33.9MB
/usr/local/venv/bin/ruff	31.8MB
/usr/share/icu/78.3/icudt78l.dat	31.5MB
/usr/lib/llvm/21/lib/libclang.so.21.1.7	30.2MB
/usr/lib/llvm/21/bin/c-index-test	28.6MB
/usr/local/venv/lib/python3.12/site-packages/gcc_arm_none_eabi/toolchain/libexec/gcc/arm-none-eabi/13.2.1/cc1	28.2MB
/usr/lib/libz3.so	27.9MB
/usr/bin/run	26.7MB
/usr/local/venv/lib/python3.12/site-packages/numpy.libs/libscipy_openblas64_-71e1b124.so	23.6MB
/usr/comma/updater	23.5MB
/usr/comma/setup	23.5MB
/usr/comma/reset	23.5MB
/usr/local/uv/python/cpython-3.12.13-linux-aarch64-gnu/bin/python3.12	22.2MB
/usr/local/uv/python/cpython-3.12.13-linux-aarch64-gnu/lib/libpython3.12.so.1.0	22.1MB

[greatgitsby]

i'm not convinced most folks will do dev through devcontainer. it is more useful to invest in infrastructure for LLMs for debug, bringup, and simplify faster