Fix live boot: custom syslinux.cfg and explicit squashfs/overlay modules

The releng syslinux.cfg references UI .c32 modules that may not load,
causing syslinux to fall back without archisolabel= in the kernel cmdline
so the archiso initrd hook scans for an empty device label and sets root=''.

- Write our own minimal syslinux.cfg using %INSTALL_DIR%/%ARCHISO_LABEL%
  placeholders; Dockerfile now only copies .c32 binaries from releng
- Add squashfs and overlay to mkinitcpio MODULES explicitly
- Remove microcode hook (no intel-ucode/amd-ucode packages installed)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

iso/docker/Dockerfile

@@ -36,10 +36,11 @@ WORKDIR /build
 COPY . /build/orionos
 
 # Bootstrap boot loader configs from the installed archiso releng profile.
-# syslinux/ is required for bios.syslinux.mbr; efiboot/ for systemd-boot UEFI.
-# Fall back to a minimal loader.conf if releng ships without efiboot/.
-RUN cp -r /usr/share/archiso/configs/releng/syslinux \
-          /build/orionos/iso/profile/ && \
+# Copy only the .c32 binary modules — our repo provides syslinux.cfg.
+# efiboot/ is needed for systemd-boot UEFI; fall back to a minimal loader.conf.
+RUN mkdir -p /build/orionos/iso/profile/syslinux && \
+    cp /usr/share/archiso/configs/releng/syslinux/*.c32 \
+       /build/orionos/iso/profile/syslinux/ 2>/dev/null || true && \
     if [ -d /usr/share/archiso/configs/releng/efiboot ]; then \
         cp -r /usr/share/archiso/configs/releng/efiboot \
               /build/orionos/iso/profile/; \

iso/profile/airootfs/etc/mkinitcpio.conf

@@ -1,4 +1,4 @@
-MODULES=()
+MODULES=(squashfs overlay)
 BINARIES=()
 FILES=()
-HOOKS=(base udev microcode archiso block filesystems keyboard)
+HOOKS=(base udev archiso block filesystems keyboard)

iso/profile/syslinux/syslinux.cfg

@@ -0,0 +1,8 @@
+DEFAULT arch64
+TIMEOUT 50
+PROMPT 0
+
+LABEL arch64
+    LINUX /%INSTALL_DIR%/boot/x86_64/vmlinuz-linux
+    INITRD /%INSTALL_DIR%/boot/x86_64/initramfs-linux.img
+    APPEND archisobasedir=%INSTALL_DIR% archisolabel=%ARCHISO_LABEL% rw