feat: scaffold Arcline OS build system

Scaffold the Arcline OS build system ("the wires"): a transparent,
auditable pipeline that turns a Debian bookworm base into hardened OS
images for the server, workstation, and cloud editions.

- Makefile orchestrates everything (make iso-<edition>, check, test,
  toolchain, clean); versions.mk is the single source of truth for
  versions and paths.
- scripts/ is the plain-bash pipeline: debootstrap -> install packages
  -> apply overlays -> in-chroot configure -> live ISO, plus a rootfs
  archive along the way.
- ARCLINE_TOOLCHAIN=auto|skip|require controls whether the 11 Go tools
  are bundled into an image (auto by default; minimal builds available
  via make iso-<edition>-minimal).
- GPL-3.0 licensed, sponsored by Arcline IT LLC.

versions.mk

@@ -0,0 +1,40 @@
+# ─────────────────────────────────────────────────────────────────────────────
+# Arcline OS — version pins & build constants
+#
+# Single source of truth for what a build produces. Every script sources this
+# (directly or via scripts/common.sh) so there is exactly one place to bump a
+# version or switch the Debian base.
+# ─────────────────────────────────────────────────────────────────────────────
+
+# Distro identity
+DISTRO_NAME   := Arcline OS
+DISTRO_ID     := arclineos
+VERSION       := 0.1.0
+RELEASE_NAME  := arclines
+
+# Debian base we build on. Bookworm = Debian 12 stable.
+DEBIAN_SUITE  := bookworm
+DEBIAN_MIRROR := http://deb.debian.org/debian
+SECURITY_MIRROR := http://security.debian.org/debian-security
+
+# Architecture we target first. amd64 is the primary; arm64 builds are a
+# stretch goal. Kept in one place so adding arm64 is a one-line change.
+ARCH          := amd64
+
+# Kernel flavour shipped by the base. Bookworm ships 6.1 LTS.
+KERNEL_PACKAGE := linux-image-amd64
+KERNEL_VERSION := 6.1
+
+# Edition codenames (the "what do I install" flavours).
+EDITIONS      := server workstation cloud
+
+# Output layout under build/
+BUILD_DIR     := build
+ROOTFS_DIR    := $(BUILD_DIR)/rootfs
+IMAGE_DIR     := $(BUILD_DIR)/iso
+DEB_DIR       := $(BUILD_DIR)/debs
+LOG_DIR       := $(BUILD_DIR)/logs
+ARTIFACT_DIR  := $(BUILD_DIR)/artifacts
+
+# Toolchain: the 11 Go tools that ship with Arcline OS (see toolchain/).
+TOOLCHAIN_REPO := https://git.arcline.it/arcline/tools.git