style: align comments with the project conventions

Apply a codebase-wide comment audit against the comment conventions:
split banned semicolons and multi-sentence lines into one sentence per
line, cut cross-file and history narration, trim file-top headers to a
single purpose line, and drop verbosity that did not earn its place.
Prose docs (CLAUDE.md, install.md) get the same one-sentence-per-line
and no-semicolon treatment.

hosts/neogaia/default.nix

@@ -5,7 +5,8 @@
   ...
 }:
 # neogaia — Dell XPS 13 9380 laptop.
-# Disk layout is in ./disk.nix; `fileSystems` are derived from it, none declared here.
+# Disk layout is in ./disk.nix.
+# `fileSystems` are derived from it, none declared here.
 {
   imports = [
     inputs.nixos-hardware.nixosModules.dell-xps-13-9380
@@ -22,10 +23,10 @@
   boot.kernelPackages = pkgs.linuxPackages_cachyos;
 
   # Redistributable firmware for the QCA6174 wifi (ath10k blobs).
-  # Intel microcode updates follow from this; none declared here.
+  # Intel microcode updates follow from this, so none is declared here.
   hardware.enableRedistributableFirmware = true;
 
-  # RAM-backed swap; no on-disk swap partition.
+  # RAM-backed swap, no on-disk swap partition.
   zramSwap.enable = true;
 
   # So wifi can be joined from the console.

hosts/neogaia/disk.nix

@@ -1,7 +1,8 @@
 { ... }:
 # neogaia's disk layout for disko: one NVMe disk, GPT, with an EFI system
-# partition and a LUKS container holding btrfs subvolumes. No swap partition;
-# swap is zram. disko derives `fileSystems` and `boot.initrd.luks.devices` from this.
+# partition and a LUKS container holding btrfs subvolumes.
+# No swap partition, since swap is zram.
+# disko derives `fileSystems` and `boot.initrd.luks.devices` from this.
 {
   disko.devices.disk.main = {
     type = "disk";
@@ -10,8 +11,8 @@
       type = "gpt";
       partitions = {
         ESP = {
-          # Each generation stores a kernel and initrd here and the CachyOS
-          # kernel is large; an exhausted partition fails bootloader installs.
+          # Each generation stores a kernel and initrd here and the CachyOS kernel is large.
+          # An exhausted partition fails bootloader installs.
           size = "2G";
           type = "EF00";
           content = {

hosts/neogaia/hardware-configuration.nix

@@ -1,6 +1,6 @@
 { lib, modulesPath, ... }:
 # Hardware detected by nixos-generate-config on this machine.
-# disko derives `fileSystems` and the LUKS device; none declared here.
+# disko derives `fileSystems` and the LUKS device, none declared here.
 {
   imports = [ (modulesPath + "/installer/scan/not-detected.nix") ];