Complete archiso/Calamares profile scaffold (iso/)

- Calamares modules: unpackfs (clone), partition/mount/fstab (btrfs subvols),
  bootloader (systemd-boot + quiet splash), packages (strip live), services
  (greetd), shellprocess (snapper, flathub, strip-live), branding (Fuji)
- bootstrap-profile.sh: releng base + linux-zen swap + overlay our deltas
- BUILD.md: build steps, decisions, and honest open items (needs build-test)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

distro/camel.toml

@@ -180,6 +180,7 @@ icons        = ["papirus-icon-theme", "adwaita-icon-theme"]
 [delivery]
 model            = "own binary repo [tanin] + official Arch repos (EndeavourOS/CachyOS style)"
 iso_tool         = "archiso"
+iso_profile      = "iso/ — releng-base + overrides; bootstrap-profile.sh assembles + builds. systemd-boot, btrfs+snapper, plymouth, linux-zen, Calamares clone-install. Scaffold; needs build-test."
 installer        = "calamares"
 calamares_target = "tanin-desktop"        # the netinstall/packages module installs just this
 dotfiles         = "tanin-setup seeds ~/.config from /usr/share/tanin/skel (never writes /home at pkg time)"