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, 49 insertions, 0 deletions

diff --git a/openspec/changes/add-host-bootstrap-script/specs/nix-flake-bootstrap/spec.md b/openspec/changes/add-host-bootstrap-script/specs/nix-flake-bootstrap/spec.md
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+## Purpose
+
+Provides a single Nix flake that provisions NixOS hosts from a copyable template and provisions a shared, cross-platform home-manager user profile that installs standalone on non-NixOS systems, keeping both paths built from the same per-user module.
+
+## ADDED Requirements
+
+### Requirement: Host directories are auto-discovered as flake outputs
+Any directory under `hosts/` other than `hosts/template` that contains a valid host definition SHALL automatically become a `nixosConfigurations.<name>` output, without requiring any edit to `flake.nix`.
+
+#### Scenario: New host directory becomes buildable without touching flake.nix
+- **WHEN** a new directory `hosts/<name>/` is created containing `configuration.nix`, `hardware-configuration.nix`, and a `system` file, and `flake.nix` itself is left unmodified
+- **THEN** `nixosConfigurations.<name>` evaluates successfully as part of the flake's outputs
+
+#### Scenario: Template remains excluded from discovery
+- **WHEN** the flake's outputs are evaluated
+- **THEN** `hosts/template` does not appear as a `nixosConfigurations` entry, regardless of its contents
+
+### Requirement: Host creation is scripted
+The system SHALL provide a script that scaffolds a new NixOS host directory from the template, given a hostname, a target root path, and a state version.
+
+#### Scenario: Scaffolding a new host
+- **WHEN** the host creation script is run with a hostname, a `--root` path, and a `--state-version`
+- **THEN** a `hosts/<hostname>/` directory is created containing a `configuration.nix` with the hostname and state version filled in, a `system` file, and a `hardware-configuration.nix` copied from the given root
+
+#### Scenario: Refusing to overwrite an existing host
+- **WHEN** the host creation script is run with a hostname that already has a `hosts/<hostname>/` directory, without an explicit override flag
+- **THEN** the script fails without modifying the existing directory
+
+### Requirement: Hardware configuration source is always explicit
+The host creation script SHALL require an explicit root path for locating `hardware-configuration.nix` and SHALL NOT read from the invoking system's own `/etc/nixos` unless that path is explicitly given as the root.
+
+#### Scenario: No root provided
+- **WHEN** the host creation script is run without a root path specified
+- **THEN** the script fails with an error rather than falling back to any default location
+
+#### Scenario: Live installer environment targets the mounted install, not the live system
+- **WHEN** the host creation script is run from a NixOS live/installer environment with `--root /mnt` pointing at a freshly mounted install target
+- **THEN** the resulting `hardware-configuration.nix` is copied from `/mnt/etc/nixos/hardware-configuration.nix`, and the live environment's own `/etc/nixos/hardware-configuration.nix` is never read
+
+#### Scenario: Hardware configuration cannot be found or generated
+- **WHEN** the host creation script is run with a `--root` path that has no `hardware-configuration.nix` and no `nixos-generate-config` command is available to create one
+- **THEN** the script fails with a clear error instead of proceeding with a missing or stub file
+
+### Requirement: Install target matches the created host name
+The host attribute produced for a newly scaffolded host SHALL exactly match the hostname given to the creation script, so the host can be installed or rebuilt via `<flake>#<hostname>`.
+
+#### Scenario: Installing a newly scaffolded host
+- **WHEN** a host is scaffolded with a given hostname
+- **THEN** `nixos-install --flake <flake-path>#<hostname>` and `nixos-rebuild switch --flake <flake-path>#<hostname>` both resolve to the configuration that was just scaffolded