Scope in-file comments to the current file state (task 0001)

Address PR review feedback: in-file comments should describe only what the
file currently is, not task numbers, external tooling, or past/future states.

- hosts/neogaia: drop the "replaced by disko in task 0002" / "arrive in later
  tasks" framing; describe the filesystems and hardware profile as the
  placeholder values they are.
- lib: drop the "no null-placeholder traversal hack" comparison to a prior
  implementation.
- system: drop "no impure environment lookup" from the user.name description
  and the sops/post-boot roadmap from the user comment.

hosts/neogaia/default.nix

@@ -1,10 +1,8 @@
 { ... }:
 # neogaia — Dell XPS 13 9380 laptop.
 #
-# Minimum viable Host: enough to evaluate and build the system toplevel. The
-# real disk layout (disko: LUKS + btrfs + zram), the CachyOS kernel, networking,
-# and the terminal Modules arrive in later tasks; the placeholders below are
-# replaced by disko in task 0002.
+# The filesystems and hardware profile below are placeholder values, not the
+# machine's real encrypted layout.
 {
   imports = [ ./hardware-configuration.nix ];
 
@@ -13,8 +11,7 @@
   boot.loader.systemd-boot.enable = true;
   boot.loader.efi.canTouchEfiVariables = true;
 
-  # Placeholder filesystems so the toplevel builds; superseded by the disko
-  # layout in task 0002.
+  # Placeholder label-based filesystems.
   fileSystems."/" = {
     device = "/dev/disk/by-label/nixos";
     fsType = "ext4";

hosts/neogaia/hardware-configuration.nix

@@ -1,7 +1,6 @@
 { lib, modulesPath, ... }:
-# Placeholder hardware profile — regenerated on the target machine at install
-# time (`nixos-generate-config` / `disko-install`). Carries only enough for the
-# toplevel to evaluate: the host platform and the XPS 13's initrd modules.
+# Placeholder hardware profile for the XPS 13: the host platform and the initrd
+# modules the machine needs to evaluate and boot.
 {
   imports = [ (modulesPath + "/installer/scan/not-detected.nix") ];
 

lib/default.nix

@@ -15,8 +15,8 @@ let
 
   # --- Auto-loader ---------------------------------------------------------
   # Recursively collect every `.nix` file under `dir`, returned as a flat list
-  # of paths suitable for a module `imports`. No null-placeholder traversal
-  # hack: a directory recurses, a `.nix` file is taken, anything else is skipped.
+  # of paths suitable for a module `imports`: a directory recurses, a `.nix`
+  # file is taken, anything else is skipped.
   collectNixFiles =
     dir:
     flatten (

system/default.nix

@@ -23,10 +23,8 @@ in
       type = types.str;
       default = "alexion";
       description = ''
-        The primary interactive user this Host is built for. An explicit option
-        with no impure environment lookup, so the config is reproducible and
-        honest about who the user is. Drives both the system account and the
-        home-manager user in lockstep.
+        The primary interactive user this Host is built for. Drives both the
+        system account and the home-manager user in lockstep.
       '';
     };
     description = mkOption {
@@ -55,9 +53,7 @@ in
     ];
     environment.systemPackages = [ pkgs.git ];
 
-    # Primary user, in wheel. The bootstrap password is set by hand at install
-    # time and never committed; moving it to a sops-backed hashedPasswordFile is
-    # the first post-boot task (out of scope for the MVI).
+    # Primary user, in wheel. No password is set here.
     users.users.${user.name} = {
       isNormalUser = true;
       description = user.description;