**Enable Nix experimental features system-wide and refactor Nix bootstrap config**

* Rename `config.sh` to `bootstrap_config.sh` to clearly separate installer bootstrap config from Nix system config
* Add `nix_conf_file.sh` to manage `/etc/nix/nix.conf` safely and idempotently
* Ensure `nix-command` and `flakes` are enabled without overwriting existing experimental features
* Invoke Nix config enforcement from `nix/init.sh` during root installation
* Update documentation and ShellCheck annotations accordingly
* Extend CLI git proxy to include `git status`

https://chatgpt.com/share/693d5c4a-bad0-800f-adaf-4719dd4ca377

scripts/nix/init.sh

@@ -1,21 +1,23 @@
 #!/usr/bin/env bash
 set -euo pipefail
 
-# shellcheck source=lib/config.sh
+# shellcheck source=lib/bootstrap_config.sh
 # shellcheck source=lib/detect.sh
 # shellcheck source=lib/path.sh
 # shellcheck source=lib/symlinks.sh
 # shellcheck source=lib/users.sh
 # shellcheck source=lib/install.sh
+# shellcheck source=lib/nix_conf_file.sh
 
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 
-source "${SCRIPT_DIR}/lib/config.sh"
+source "${SCRIPT_DIR}/lib/bootstrap_config.sh"
 source "${SCRIPT_DIR}/lib/detect.sh"
 source "${SCRIPT_DIR}/lib/path.sh"
 source "${SCRIPT_DIR}/lib/symlinks.sh"
 source "${SCRIPT_DIR}/lib/users.sh"
 source "${SCRIPT_DIR}/lib/install.sh"
+source "${SCRIPT_DIR}/lib/nix_conf_file.sh"
 
 echo "[init-nix] Starting Nix initialization..."
 
@@ -26,6 +28,7 @@ main() {
     ensure_nix_on_path
 
     if [[ "${EUID:-0}" -eq 0 ]]; then
+      nixconf_ensure_experimental_features
       ensure_global_nix_symlinks "$(resolve_nix_bin 2>/dev/null || true)"
     else
       ensure_user_nix_symlink "$(resolve_nix_bin 2>/dev/null || true)"
@@ -106,6 +109,10 @@ main() {
   # -------------------------------------------------------------------------
   ensure_nix_on_path
 
+  if [[ "${EUID:-0}" -eq 0 ]]; then
+    nixconf_ensure_experimental_features
+  fi
+
   local nix_bin_post
   nix_bin_post="$(resolve_nix_bin 2>/dev/null || true)"