switch kernel build to patch-based approach

- PKGBUILD is now generated by patching upstream Arch linux PKGBUILD
- pkg/linux-aios/ contains only aios.patch
- cfg/repo.sh clones upstream, applies patch, builds
- Update CLAUDE.md with full documentation

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cfg/repo.sh

@@ -64,13 +64,32 @@ if [[ "$BUILD_KERNEL" == "true" ]]; then
 
   ssh "$HOST_KERNEL" zsh -s <<'KERNEL_REMOTE'
 set -e
+REPOS="${HOME}/repos"
 WORK="${HOME}/aios-kernel"
+
+# Clone or update upstream Arch linux PKGBUILD
+mkdir -p "$REPOS"
+if [ -d "$REPOS/archlinux" ]; then
+  cd "$REPOS/archlinux"
+  git pull
+else
+  git clone --depth 1 https://gitlab.archlinux.org/archlinux/packaging/packages/linux.git "$REPOS/archlinux"
+fi
+
+# Prepare workspace
 rm -rf "$WORK"
-mkdir -p "$WORK"
+mkdir -p "$WORK/linux-aios"
+cp "$REPOS/archlinux/PKGBUILD" "$WORK/linux-aios/"
+cp "$REPOS/archlinux/config.x86_64" "$WORK/linux-aios/"
+
+# Clone aios repo for patch
 cd "$WORK"
 git clone --depth 1 https://git.syui.ai/ai/os.git
-cp -r "$WORK/os/pkg/linux-aios" "$WORK/linux-aios"
+
+# Apply aios patch
 cd "$WORK/linux-aios"
+patch -p1 < "$WORK/os/pkg/linux-aios/aios.patch"
+
 makepkg -sf --noconfirm --skippgpcheck
 echo "=== Kernel built ==="
 KERNEL_REMOTE