dev: NixOS 25.11 매뉴얼 로컬 사본 추가

nixpkgs nixos-25.11 브랜치의 nixos/doc/manual/ 디렉토리를 sparse clone으로
가져와 ~/obsidian/dev/nixos-manual/에 복사. _index.md에 구조/갱신 방법 정리.

오프라인 참조 + AI 에이전트 컨텍스트용. sandbox-tokyo 같은 NixOS 노드 운영 시
빠른 참조로 사용.

dev/nixos-manual/development/meta-attributes.section.md

@@ -0,0 +1,73 @@
+# Meta Attributes {#sec-meta-attributes}
+
+Like Nix packages, NixOS modules can declare meta-attributes to provide
+extra information. Module meta attributes are defined in the `meta.nix`
+special module.
+
+`meta` is a top level attribute like `options` and `config`. Available
+meta-attributes are `maintainers`, `doc`, and `buildDocsInSandbox`.
+
+Each of the meta-attributes must be defined at most once per module
+file.
+
+```nix
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+{
+  options = {
+    # ...
+  };
+
+  config = {
+    # ...
+  };
+
+  meta = {
+    maintainers = with lib.maintainers; [ ];
+    doc = ./default.md;
+    buildDocsInSandbox = true;
+  };
+}
+```
+
+-   `maintainers` contains a list of the module maintainers.
+
+-   `doc` points to a valid [Nixpkgs-flavored CommonMark](
+      https://nixos.org/manual/nixpkgs/unstable/#sec-contributing-markup
+    ) file containing the module
+    documentation. Its contents is automatically added to
+    [](#ch-configuration). Changes to a module documentation have to
+    be checked to not break building the NixOS manual:
+
+    ```ShellSession
+    $ nix-build nixos/release.nix -A manual.x86_64-linux
+    ```
+
+-  `buildDocsInSandbox` indicates whether the option documentation for the
+   module can be built in a derivation sandbox. This option is currently only
+   honored for modules shipped by nixpkgs. User modules and modules taken from
+   `extraModules` are always built outside of the sandbox, as has
+   been the case in previous releases.
+
+   Building NixOS option documentation in a sandbox allows caching of the built
+   documentation, which greatly decreases the amount of time needed to evaluate
+   a system configuration that has NixOS documentation enabled. The sandbox also
+   restricts which attributes may be referenced by documentation attributes
+   (such as option descriptions) to the `options` and `lib` module arguments and
+   the `pkgs.formats` attribute of the `pkgs` argument, `config` and the rest of
+   `pkgs` are disallowed and will cause doc build failures when used. This
+   restriction is necessary because we cannot reproduce the full nixpkgs
+   instantiation with configuration and overlays from a system configuration
+   inside the sandbox. The `options` argument only includes options of modules
+   that are also built inside the sandbox, referencing an option of a module
+   that isn't built in the sandbox is also forbidden.
+
+   The default is `true` and should usually not be changed; set it to `false`
+   only if the module requires access to `pkgs` in its documentation (e.g.
+   because it loads information from a linked package to build an option type)
+   or if its documentation depends on other modules that also aren't sandboxed
+   (e.g. by using types defined in the other module).