Drop the zram Module and enable zram inline on neogaia

modules/zram.nix only wrapped the native zramSwap.enable toggle without
adding anything. Rewrite the touched comments to describe only the current
file content, and record the in-file-comment convention in CLAUDE.md.

.claude/tasks/0003-kernel-and-hardware.md

@@ -15,7 +15,7 @@ The kernel is selected through a small per-`Host` kernel mechanism so other `Hos
 - [x] The chaotic substituter and trusted public key are in the Nix settings, so the kernel is fetched from cache rather than compiled.
 - [x] Intel microcode is enabled.
 - [x] Redistributable firmware is enabled so the QCA6174 wifi hardware is available.
-- [x] A zram toggle `Module` exists (following the `Enable convention`) and is enabled on `neogaia`.
+- [-] A zram toggle `Module` exists (following the `Enable convention`) and is enabled on `neogaia`. — Module dropped in PR review; zram is enabled inline on `neogaia` instead (see notes).
 - [x] The `neogaia` toplevel still builds with all of the above.
 
 ## Implementation Notes
@@ -23,5 +23,4 @@ The kernel is selected through a small per-`Host` kernel mechanism so other `Hos
 - **Per-`Host` kernel mechanism = native `boot.kernelPackages`.** neogaia sets `boot.kernelPackages = pkgs.linuxPackages_cachyos` directly in its Host directory (`hosts/neogaia/default.nix`). No custom wrapper option was added: `boot.kernelPackages` is already a per-`Host` setting, so other `Host`s pick their own kernel the same way. A string→package wrapper would have been premature abstraction with one `Host` and one kernel, so it was deliberately left out; the "mechanism" is the per-`Host` placement of the native option.
 - **Substituter/key live in the shared base, via the `extra-` options.** They were added to `system/default.nix` (shared by every `Host`), not just neogaia, because the chaotic module is wired for all `Host`s and the cache is general plumbing. `nix.settings.extra-substituters` / `extra-trusted-public-keys` are used rather than the replacing `substituters` / `trusted-public-keys`, so `cache.nixos.org` (and any other substituter) is only appended to, never dropped. chaotic's own module also provides these entries; the explicit declaration is belt-and-suspenders and keeps the built system's cache config visible and independent of that module.
 - **Dev-host build needed a daemon-level cache.** Building the toplevel here first compiled the CachyOS kernel (and rustc bootstrap) from source, because the build daemon's `/etc/nix/nix.conf` had no `nyx-cache` substituter — the built system's `nix.settings` do not govern the daemon doing the build, and the dev user is a non-trusted client that cannot add substituters from the CLI. Adding `extra-substituters`/`extra-trusted-public-keys` for `nyx-cache` to `/etc/nix/nix.conf` (sudo) and restarting `nix-daemon` fixed it; the build then fetched the kernel (7.1.3) from the cache. Recorded as a gotcha in `CLAUDE.md`.
-- **zram `Module` kept minimal.** `modules/zram.nix` is a pure toggle (`zramSwap.enable = true` under `mkIf`), following the `modules/example.nix` reference shape. This preserves task 0002's exact behaviour while moving the switch behind the `Enable convention`; the direct `zramSwap.enable = true` previously inline in the `Host` was removed in favour of `modules.zram.enable = true`.
-- **Why zram graduated to a `Module` but kernel/microcode/firmware stayed inline.** zram is a reusable, cross-`Host` feature toggle (the spec calls for it as a `Module`), whereas the kernel choice, Intel microcode, and firmware are neogaia-specific hardware facts that belong to the `Host` itself.
+- **zram is enabled inline, not as a `Module` (criterion 5 dropped).** The task asked for a zram toggle `Module`, and one was built first (`modules/zram.nix`), but PR review rejected it as a single-line abstraction that wraps the native `zramSwap.enable` toggle without adding anything. It was removed, and `neogaia` sets `zramSwap.enable = true` directly, as it did before task 0003. The `Enable convention` reference remains `modules/example.nix`; real feature `Module`s arrive with fish/tmux/nvim/Claude Code in later tasks.

CLAUDE.md

@@ -3,6 +3,13 @@
 One flake that builds every machine the user owns.
 The domain model (Host, Module, Skeleton, Auto-loader, Enable convention, overlays) lives in `.claude/CONTEXT.md`; the current deliverable's spec is `.claude/spec/laptop-mvi.md`.
 
+## Conventions
+
+- In-file comments describe only the current content and behaviour of the file they sit in.
+  Do not write comments about history ("used to be X", "now moved here"), about how a value is consumed in other files, or that justify the choice against alternatives.
+  Never reference agent-facing state (anything under `.claude/` or `CLAUDE.md`) from a code comment: that state is not part of understanding the code.
+  A reader looking at only that file should find every comment accurate and self-contained.
+
 ## Gotchas
 
 - Nix on the dev host needs experimental features passed per-command.

hosts/neogaia/default.nix

@@ -17,10 +17,7 @@
   boot.loader.systemd-boot.enable = true;
   boot.loader.efi.canTouchEfiVariables = true;
 
-  # Kernel is a per-Host choice, expressed through boot.kernelPackages: neogaia
-  # runs the CachyOS kernel from chaotic-nyx (fetched from the chaotic binary
-  # cache wired in system/, not compiled from source). Other Hosts pick their
-  # own kernel the same way, so the choice never leaves the Host.
+  # neogaia runs the CachyOS kernel, selected per-Host via boot.kernelPackages.
   boot.kernelPackages = pkgs.linuxPackages_cachyos;
 
   # Intel CPU microcode updates for the XPS 13's Core i7-8565U.
@@ -29,7 +26,6 @@
   # Redistributable firmware — carries the ath10k blobs the QCA6174 wifi needs.
   hardware.enableRedistributableFirmware = true;
 
-  # Swap is RAM-backed zram (the zram Module) rather than an on-disk partition,
-  # matching the disko layout, which declares no swap partition.
-  modules.zram.enable = true;
+  # Swap is RAM-backed zram rather than an on-disk partition.
+  zramSwap.enable = true;
 }

modules/zram.nix

@@ -1,14 +0,0 @@
-{ config, lib, ... }:
-# A toggle for RAM-backed swap. A Host that has no on-disk swap partition (like
-# neogaia, whose disko layout deliberately omits one) enables this to get a
-# compressed zram device instead.
-let
-  cfg = config.modules.zram;
-in
-{
-  options.modules.zram.enable = lib.mkEnableOption "zram-backed compressed swap";
-
-  config = lib.mkIf cfg.enable {
-    zramSwap.enable = true;
-  };
-}

system/default.nix

@@ -52,13 +52,9 @@ in
       "flakes"
     ];
 
-    # The chaotic binary cache, declared explicitly on the built system so the
-    # CachyOS kernel is substituted rather than compiled. chaotic's own module
-    # also provides these, but stating them here keeps the built system's cache
-    # config visible and independent of that module. Added via the `extra-`
-    # options so they only append — cache.nixos.org and any other substituter
-    # are never dropped. (Fetching at install time depends on the installing
-    # daemon's substituters, not this — see the chaotic gotcha in CLAUDE.md.)
+    # The chaotic binary cache, so the CachyOS kernel is substituted rather than
+    # compiled. Appended with the `extra-` options so cache.nixos.org and any
+    # other substituter are kept alongside it.
     nix.settings.extra-substituters = [ "https://nyx-cache.chaotic.cx/" ];
     nix.settings.extra-trusted-public-keys = [
       "nyx-cache.chaotic.cx:dJxTrgMC3V3cFfyIiBQDQorG6k1LsqurH/srpMSq7qk="