Add Zero-OS customization before CPIO creation

- Add initramfs_finalize_customization() function
- Remove root password for passwordless login (sed -i 's/^root:[^:]*:/root::/' /etc/passwd)
- Update /etc/motd and /etc/issue to Zero-OS branding instead of Alpine
- Called automatically before CPIO creation
- Fixes init script duplication issue (/init vs /sbin/init)
- Correct boot flow: /init → switch_root → /sbin/zinit init (no /sbin/init needed)

.gitignore

@@ -5,6 +5,7 @@ components/
 initramfs/
 kernel/
 dist/
+.build-stages/
 
 # Build logs
 *.log
@@ -36,5 +37,4 @@ linux-*.tar.xz
 
 # OS generated files
 .DS_Store
-Thumbs.db# Build stage tracking (should not be in git)
-.build-stages/
+Thumbs.db