docs: add repo layout, module catalogue and add-a-host guide

README.md

@@ -12,16 +12,67 @@ Defined in the host table in [`flake.nix`](./flake.nix):
 | `lyrathorpe-mbp`      | `aarch64-linux`  | MacBook Pro (Apple Silicon, Asahi)                                                                          |
 | `lyrathorpe-t400`     | `x86_64-linux`   | ThinkPad T400 — [install notes](./hosts/T400/README.md)                                                     |
 | `lyrathorpe-macpro31` | `x86_64-linux`   | Mac Pro 3,1, desktop — [install notes](./hosts/MacPro31/README.md)                                          |
-| `emmathorpe-edaas`    | `x86_64-linux`   | Work WSL box (NixOS-WSL)                                                                                    |
+| `emmathorpe-edaas`    | `x86_64-linux`   | Work WSL box (NixOS-WSL) — [notes](./hosts/EDaaS/README.md)                                                 |
 | `lyrathorpe-rpi5`     | `aarch64-linux`  | Raspberry Pi 5 headless server: Docker host + nginx reverse proxy — [install notes](./hosts/RPi5/README.md) |
-| `lyrathorpe-mac`      | `aarch64-darwin` | macOS (nix-darwin)                                                                                          |
+| `lyrathorpe-mac`      | `aarch64-darwin` | macOS (nix-darwin) — [notes](./hosts/Darwin/README.md)                                                      |
 
 Shared layers: `home` (home-manager: shell, git, editor),
 `modules/common-nixos.nix` (all NixOS hosts: fonts, nix-ld, caches),
 `modules/workstation.nix` (physical graphical hosts: audio, thermald,
 earlyoom, fwupd), `modules/laptop.nix` (laptops: Wi-Fi, Bluetooth, power,
-lid), and `modules/ssh.nix` (key-only sshd). The x86 hosts also pull
+lid), `modules/desktop.nix` (wired desktops: NetworkManager), and
-`nixos-hardware` profiles.
+`modules/ssh.nix` (key-only sshd). The x86 hosts also pull `nixos-hardware`
+profiles. The full module catalogue is below.
+
+## Repository layout
+
+```
+flake.nix              # inputs, mkHost/mkDarwinHost, the host tables, dev shell + checks
+flake.lock             # pinned input revisions (Renovate keeps this fresh)
+modules/               # reusable NixOS system modules (see "Module catalogue")
+home/                  # home-manager profile: shell, git, editor, claude, desktop, sway
+users/                 # identity registry + per-user home extras (see "Users")
+hosts/<Name>/          # per-machine config: configuration.nix + hardware-configuration.nix
+lib/                   # small pure helpers (currently the Catppuccin Mocha palette)
+.gitea/workflows/      # CI (nix flake check + per-host eval)
+statix.toml            # lint config (house-style lints disabled)
+.editorconfig          # base whitespace style
+tf-inspect/            # UNRELATED scratch project (gitignored, its own git repo);
+                       #   RouterOS / home-services Terraform, not part of this flake
+```
+
+Each `nixosConfiguration` / `darwinConfiguration` is assembled in `flake.nix`
+from three layers: the shared `baseModules` (or `darwinBaseModules`), the
+per-form-factor and `nixos-hardware` modules listed in the host table, and the
+per-machine `hosts/<Name>/configuration.nix`. Home-manager is wired in as a
+system module; each user's home is composed from the `homeModules` list in that
+host's table entry.
+
+## Module catalogue
+
+Reusable NixOS modules under [`modules/`](./modules). "Imported by" says how a
+module reaches a host: **baseModules** (every NixOS host, via `flake.nix`),
+**host table** (listed explicitly per host in `flake.nix`), or **transitively**
+(pulled in by another module's `imports`).
+
+| Module               | Imported by                             | What it does / when to use it                                                                                                                                                                    |
+| -------------------- | --------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| `common-nixos.nix`   | baseModules (all NixOS)                 | Timezone/locale, store hygiene (auto-optimise, big download buffer, **no** auto-GC), the nix-community binary cache, `nix-ld`, base CLI (`git`, `fastfetch`), and the fleet-wide font stack.     |
+| `users.nix`          | baseModules (all NixOS)                 | Builds `users.users` from the registry for the host's `hostUsers`; enables zsh; enables Firefox + Thunderbird **only** when `features.swayDesktop.enable` is on. Applies per-user `linger`.       |
+| `features.nix`       | baseModules (all NixOS)                 | Declares feature-flag options (currently `features.swayDesktop.enable`) so any host can read/set them without importing the heavy implementation module.                                          |
+| `workstation.nix`    | transitively (via laptop/desktop)       | Form-factor-agnostic base for physical graphical hosts: turns on `swayDesktop`, Dvorak console, PipeWire, firewall (default-deny), fstrim, earlyoom, fwupd, thermald (x86), redistributable fw.  |
+| `laptop.nix`         | host table (MBP, T400)                  | `imports` workstation.nix, then adds the portable bits: iwd Wi-Fi, lid suspend/lock, Bluetooth + blueman.                                                                                        |
+| `desktop.nix`        | host table (Mac Pro)                    | `imports` workstation.nix, then swaps Wi-Fi for wired NetworkManager. Pair with `portable = false` in the host table.                                                                            |
+| `sway.nix`           | host table (graphical hosts)            | Implementation of `features.swayDesktop`: the system Sway package, the greetd/ReGreet (cage) greeter forced to Dvorak, xdg-portal, Wayland utility packages. Home-side Sway config is in `home/sway.nix`. |
+| `ssh.nix`            | host table (T400, Mac Pro, RPi5)        | Enables sshd, opens port 22, enforces a key-only policy (no password / keyboard-interactive, no root). Authorized keys come from the registry via `users.nix`.                                    |
+| `firmware/`          | referenced by MBP host config           | Committed Apple peripheral firmware blobs for the Asahi MBP (see "MacBook (Asahi) firmware").                                                                                                     |
+
+Form-factor decision: a **laptop** imports `laptop.nix` (default
+`portable = true`); a **wired desktop** imports `desktop.nix` and sets
+`portable = false`; a **headless server** imports neither (leaves
+`features.swayDesktop.enable` at its default `false`) and adds only what it
+serves. `portable` is threaded through to `home/sway.nix`, which drops the
+battery block and brightness keys on desktops.
 
 ## Users
 
@@ -38,6 +89,16 @@ Identity is data, kept separate from the reusable modules:
   identity into that user's home config as the `identity` module arg. A host can
   therefore declare any number of users.
 
+Per-user home extras live under `users/<name>/`:
+
+- [`users/lyrathorpe/home.nix`](./users/lyrathorpe/home.nix) — personal extras
+  (an ssh host shortcut, gammastep coordinates); imported on Lyra's hosts.
+- [`users/emmathorpe/work.nix`](./users/emmathorpe/work.nix) — the work
+  toolchain (kubectl/helm/az/etc.), work-only LSP servers, and the corporate ssh
+  handling; imports
+  [`users/emmathorpe/renovate-review.nix`](./users/emmathorpe/renovate-review.nix),
+  the daily headless Renovate-PR review timer (EDaaS only).
+
 ### Portable home (off-NixOS / external consumers)
 
 The home config is also exposed for use beyond these hosts:
@@ -61,6 +122,36 @@ sudo nixos-rebuild switch --flake .#<configuration>
 darwin-rebuild switch --flake .#lyrathorpe-mac
 ```
 
+On a host whose `networking.hostName` matches its flake attribute (the WSL box
+and the Pi are set up this way), `nh os switch` resolves the configuration from
+the hostname with no `--flake`/`-H` flag.
+
+## Adding a new host
+
+1. **Create `hosts/<Name>/`.** Add `configuration.nix` with the host-specific
+   bits only: `networking.hostName`, bootloader (firmware-specific — it is
+   deliberately not set in the shared modules), and any per-machine hardware
+   quirks. Keep anything reusable in `modules/` instead.
+2. **Hardware config.** Generate `hardware-configuration.nix` on the real
+   machine with `nixos-generate-config` and commit it. If the machine does not
+   exist yet, commit a clearly-labelled placeholder so the host still evaluates
+   in CI (see the existing T400 / RPi5 placeholders), and replace it at install.
+   These files are excluded from the formatter and linters.
+3. **Add a host-table entry in `flake.nix`.** Under `hosts` (NixOS) or
+   `darwinHosts` (macOS), set `system`, the `modules` list (host config + form
+   factor + any `nixos-hardware` profiles), and the `users` map (each user's
+   `homeModules`). Choose the form factor per the decision note above; a headless
+   host imports neither `laptop.nix` nor `desktop.nix`.
+4. **Users.** If the host introduces a new person, add them to
+   `users/registry.nix` first; otherwise reference an existing username.
+5. **Verify.** `nix flake check` formats, lints, and evaluates every host —
+   including the new one — so a broken entry fails locally before CI. Then
+   `sudo nixos-rebuild switch --flake .#<configuration>` on the machine.
+
+No change to CI is needed: the host-eval step discovers hosts from the flake
+(`attrNames` of the configuration sets), so a new entry is picked up
+automatically.
+
 ## Shell environment & keybindings
 
 - Interactive shell features (zsh, tmux, git, ssh, CLI tools, auto-tmux):
@@ -111,4 +202,7 @@ A dev shell and a formatting/lint gate are wired through the flake:
 
 [`.gitea/workflows/ci.yaml`](./.gitea/workflows/ci.yaml) runs `nix flake check`
 (formatting, `deadnix`, `statix`, the pre-commit hooks) and evaluates every
-NixOS and Darwin host configuration on push/PR.
+NixOS and Darwin host configuration on push/PR. It always runs (no `paths:`
+filter) so the required check never hangs pending; the heavy Nix steps are
+skipped when a PR touches no `.nix`/lockfile/workflow file, and the job still
+reports green.