Add literate programming phase 1 documentation for:
- main.sh: wrapper orchestration and user journey
- config.sh: configuration management and defaults
- sanity.sh: preflight safety checks
Decision: UEFI-only support to reduce complexity. BIOS would
require separate /boot partition and additional testing burden
disproportionate to modern hardware usage.
Decision: LUKS2 as default encryption for improved security
tooling, with clear guidance for LUKS1 fallback if GRUB boot
fails. Auto-detection rejected due to version fragmentation.
Decision: Interactive configuration as default. Presets are
out of scope for phase 1 to keep the flow understandable.
The user journey documents the complete end-to-end flow from
live medium boot to first encrypted boot, establishing clear
handoff points between wrapper and installer.
