Establish project foundation: domain model, MVI spec, environment reference

Capture the design work for the NixOS migration before any implementation:

- .claude/CONTEXT.md: domain glossary (Host, Module, Skeleton, Auto-loader,
  Enable convention, unstable/stable overlay)
- .claude/adr/0001-sops-nix-for-secrets.md: secrets tooling decision
- .claude/spec/laptop-mvi.md: frozen minimum-viable-install spec for neogaia

- reference/: read-only snapshot of the current CachyOS configs (secrets and
  state excluded), plus ENVIRONMENT.md profiling the live environment to guide
  replication

reference/home/.config/fish/completions/dot.fish

@@ -0,0 +1,34 @@
+function __dot_custom_subcommands
+    echo init
+    echo help
+    path basename $HOME/.config/dot/commands/*.fish 2>/dev/null | path change-extension ''
+
+    for d in $HOME/.config/dot/commands/*/
+        test -d $d; or continue
+        set -l name (path basename $d)
+        test -f $d$name.fish; or continue
+        echo $name
+    end
+end
+
+complete -c dot -n __fish_use_subcommand -a "(__dot_custom_subcommands)"
+
+# --- dot install ---
+complete -c dot -n "__fish_seen_subcommand_from install; and not __fish_seen_argument -l restore" -l restore -d "reinstall every package from the saved list"
+complete -c dot -n "__fish_seen_subcommand_from install; and not __fish_seen_argument -l no-sync" -l no-sync -d "skip the pacman -Sy database refresh"
+complete -c dot -n "__fish_seen_subcommand_from install; and not __fish_seen_argument -l restore" -f -a "(__fish_print_pacman_packages)"
+
+# --- dot setup ---
+complete -c dot -n "__fish_seen_subcommand_from setup; and not __fish_seen_subcommand_from folders help" -f -a folders -d "bring the 8 standard XDG user directories under the short-name convention"
+complete -c dot -n "__fish_seen_subcommand_from setup; and not __fish_seen_subcommand_from folders help" -f -a help -d "show usage"
+complete -c dot -n "__fish_seen_subcommand_from setup; and __fish_seen_subcommand_from folders" -f -a help -d "show usage"
+
+# --- dot kde ---
+complete -c dot -n "__fish_seen_subcommand_from kde; and not __fish_seen_subcommand_from apply diff save help" -f -a apply -d "push manifest entries onto the live system"
+complete -c dot -n "__fish_seen_subcommand_from kde; and not __fish_seen_subcommand_from apply diff save help" -f -a diff -d "scan for settings whose live value differs from its default"
+complete -c dot -n "__fish_seen_subcommand_from kde; and not __fish_seen_subcommand_from apply diff save help" -f -a save -d "write live KDE settings into the manifest"
+complete -c dot -n "__fish_seen_subcommand_from kde; and not __fish_seen_subcommand_from apply diff save help" -f -a help -d "show usage"
+complete -c dot -n "__fish_seen_subcommand_from kde; and __fish_seen_subcommand_from apply diff save" -f -a help -d "show usage"
+# Sourced live from the schema mapping table (real .kcfg files), not a
+# hardcoded list -- same helper kde.py's own save/refresh logic builds from.
+complete -c dot -n "__fish_seen_subcommand_from kde; and __fish_seen_subcommand_from save" -f -a "(python3 $HOME/.config/dot/commands/kde/kde.py complete 2>/dev/null)"