Add scripted host bootstrapping with directory-driven discovery

nixosConfigurations now auto-discovers hosts/<name>/ directories instead
of a hand-maintained attrset, and scripts/bootstrap-host.sh (exposed as
`nix run .#bootstrap-host`) scaffolds a new host from the template. The
script always requires an explicit --root for hardware-configuration.nix
so a live-installer run can never read the live ISO's own /etc/nixos by
accident. Also records the belated task-11.1 checkbox update for the
prior change's already-committed state.

1 files changed, 18 insertions, 18 deletions

diff --git a/README.md b/README.md
index 881b2e9..3688c88 100644
--- a/README.md
+++ b/README.md
@@ -9,33 +9,33 @@ A single Nix flake for provisioning both NixOS hosts and non-NixOS systems (any
 - `modules/nixos/common.nix` — shared NixOS-only system settings applied to every NixOS host
 - `modules/home/` — the shared, cross-platform home-manager profile (shell, git, editor, CLI tools). The same modules are consumed whether activated via a NixOS host's home-manager module or standalone `home-manager switch`
 - `users/tom.nix` — identity/profile file consumed by both `mkNixos` and `mkHome`
-- `hosts/template/` — a copy-source-only NixOS host skeleton; **never** wired into `flake.nix` outputs directly. Copy it to `hosts/<real-hostname>/` when provisioning a real machine
+- `hosts/template/` — a copy-source-only NixOS host skeleton; **never** wired into `flake.nix` outputs directly (excluded from discovery by name — see below). Copy it via `scripts/bootstrap-host.sh` (or `nix run .#bootstrap-host`) when provisioning a real machine
+- `scripts/bootstrap-host.sh` — scaffolds a new `hosts/<hostname>/` from the template; exposed as `apps.<system>.bootstrap-host`
+
+Any directory under `hosts/` other than `hosts/template` that contains a `system` file automatically becomes a real `nixosConfigurations.<name>` output — adding a host means dropping in a directory, not editing `flake.nix`.
 
 ## Installing NixOS on a new machine
 
 This flake does not partition disks for you — do that first, with the standard NixOS installer or manually.
 
 1. Partition and format disks; mount the target filesystems under `/mnt` (including `/mnt/boot` for the ESP if UEFI).
-2. Generate hardware config: `nixos-generate-config --root /mnt`. Keep the generated `hardware-configuration.nix`; discard its `configuration.nix`.
-3. Get this repo onto the installer: `nix-shell -p git && git clone <your-remote-url> ~/nix-config` (requires the repo already pushed to a remote — see Follow-ups below).
-4. Copy the template into a real host: `cp -r ~/nix-config/hosts/template ~/nix-config/hosts/<real-hostname>`.
-5. Edit `hosts/<real-hostname>/configuration.nix`: set `networking.hostName`, pick the correct boot loader stanza, set `system.stateVersion` to the installer's NixOS release.
-6. Replace the stub hardware config: `cp /mnt/etc/nixos/hardware-configuration.nix ~/nix-config/hosts/<real-hostname>/hardware-configuration.nix`.
-7. Add the host to `flake.nix`:
-   ```nix
-   nixosConfigurations.<real-hostname> = lib.mkNixos {
-     hostname = "<real-hostname>";
-     system = "x86_64-linux";
-   };
+2. Get this repo onto the installer: `nix-shell -p git && git clone <your-remote-url> ~/nix-config` (requires the repo already pushed to a remote — see Follow-ups below).
+3. From `~/nix-config`, scaffold the host:
+   ```
+   nix run .#bootstrap-host -- <real-hostname> --root /mnt --state-version <ver>
    ```
-8. `cd ~/nix-config && git add -A` (flakes only see git-tracked files).
-9. If needed: `export NIX_CONFIG="experimental-features = nix-command flakes"`.
-10. `nixos-install --root /mnt --flake ~/nix-config#<real-hostname>`.
-11. Reboot and remove the install media.
-12. Afterwards, clone the flake to a stable path (e.g. `/etc/nix-config`) so future updates are just `sudo nixos-rebuild switch --flake /etc/nix-config#<real-hostname>`.
+   `--root /mnt` tells the script to read (or generate, via `nixos-generate-config --root /mnt` if needed) `hardware-configuration.nix` from the freshly mounted install target — it never reads the live installer's own `/etc/nixos`, since `--root` has no default and must always be given explicitly. `--state-version` should match the installer's NixOS release (e.g. `24.05`) and should never be changed after the fact.
+4. Review `hosts/<real-hostname>/configuration.nix` (boot loader choice, etc.) — the script prints this reminder along with the exact next commands.
+5. `cd ~/nix-config && git add hosts/<real-hostname>` (flakes only see git-tracked files).
+6. If needed: `export NIX_CONFIG="experimental-features = nix-command flakes"`.
+7. `nixos-install --root /mnt --flake ~/nix-config#<real-hostname>`.
+8. Reboot and remove the install media.
+9. Afterwards, clone the flake to a stable path (e.g. `/etc/nix-config`) so future updates are just `sudo nixos-rebuild switch --flake /etc/nix-config#<real-hostname>`.
 
 ## Installing on a non-NixOS system (any Linux, or macOS once supported)
 
+Non-NixOS hosts are unaffected by `bootstrap-host` — there's nothing per-host to scaffold, since `homeConfigurations."tom@linux"` is one generic entry shared by every standalone machine.
+
 1. Install Nix. Recommended: the [Determinate Systems installer](https://github.com/DeterminateSystems/nix-installer) (flakes enabled by default). The official installer also works, but you'll need to add `experimental-features = nix-command flakes` to `nix.conf` yourself.
 2. `git clone <your-remote-url> ~/nix-config`.
 3. First run: `nix run home-manager/master -- switch --flake ~/nix-config#tom@linux`. After that, `home-manager switch --flake ~/nix-config#tom@linux` works directly.
@@ -46,7 +46,7 @@ This only touches your home directory — no sudo required.
 
 - `nix fmt` — format all `.nix` files with `nixfmt-rfc-style`.
 - `nix develop` — a shell with `statix` and `deadnix` for linting.
-- `nix flake check` — validates `homeConfigurations."tom@linux"` and the other outputs defined here (there are no `nixosConfigurations` yet — see Follow-ups).
+- `nix flake check` — validates `homeConfigurations."tom@linux"`, `apps.bootstrap-host`, and the other outputs defined here (there are no real `nixosConfigurations` until a host is scaffolded — see Follow-ups).
 
 ## Follow-ups (not covered by this change)