initramfs: anchor relative paths to PROJECT_ROOT in [bash.initramfs_validate()](scripts/lib/initramfs.sh:799) and [bash.initramfs_create_cpio()](scripts/lib/initramfs.sh:688) to avoid CWD drift. Add diagnostics logs.
kernel: anchor kernel output path to PROJECT_ROOT in [bash.kernel_build_with_initramfs()](scripts/lib/kernel.sh:174) to ensure dist/vmlinuz.efi is under PROJECT_ROOT/dist.
helper: add [scripts/rebuild-after-zinit.sh](scripts/rebuild-after-zinit.sh) to incrementally rebuild after zinit/modules.conf/init changes. Default: initramfs-only (recreates cpio). Flags: --with-kernel, --refresh-container-mods, --run-tests. Uses --rebuild-from=initramfs_create when rebuilding kernel.
init: add early debug shell on kernel param initdebug=true; prefer /init-debug when present else spawn /bin/sh -l. See [config/init](config/init:1).
modules(stage1): add USB keyboard support (HID + host controllers) in [config/modules.conf](config/modules.conf:1): usbhid, hid_generic, hid, xhci/ehci/ohci/uhci.
