style: trim verbose comments to concise, self-contained notes

Cut restated "what", domain-glossary framing, cross-file consumption
narration, and against-alternative justification from in-file comments;
keep only non-obvious "why" and load-bearing pointers. Drop the
`generateCompletions` line (a no-op restatement of the upstream default)
and its comment.

modules/example.nix

@@ -1,12 +1,11 @@
 { config, lib, ... }:
-# The Auto-loader reference example. Every real Module copies this shape: it is
-# imported unconditionally but its body stays inert until a Host sets the
-# `enable` flag, so each Host reads as a checklist of `enable = true` lines.
+# Reference example for the module shape: imported unconditionally, but inert
+# until a host sets its `enable` flag.
 let
   cfg = config.modules.example;
 in
 {
-  options.modules.example.enable = lib.mkEnableOption "the Auto-loader reference example Module";
+  options.modules.example.enable = lib.mkEnableOption "the reference example module";
 
   config = lib.mkIf cfg.enable {
     environment.etc."skeleton-example".text = "This Module is enabled.\n";