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/configuration/network-manager.section.md

@@ -0,0 +1,46 @@
+# NetworkManager {#sec-networkmanager}
+
+To facilitate network configuration, some desktop environments use
+NetworkManager. You can enable NetworkManager by setting:
+
+```nix
+{ networking.networkmanager.enable = true; }
+```
+
+some desktop managers (e.g., GNOME) enable NetworkManager automatically
+for you.
+
+All users that should have permission to change network settings must
+belong to the `networkmanager` group:
+
+```nix
+{ users.users.alice.extraGroups = [ "networkmanager" ]; }
+```
+
+NetworkManager is controlled using either `nmcli` or `nmtui`
+(curses-based terminal user interface). See their manual pages for
+details on their usage. Some desktop environments (GNOME, KDE) have
+their own configuration tools for NetworkManager. On XFCE, there is no
+configuration tool for NetworkManager by default: by enabling
+[](#opt-programs.nm-applet.enable), the graphical applet will be
+installed and will launch automatically when the graphical session is
+started.
+
+::: {.note}
+`networking.networkmanager` and `networking.wireless` (WPA Supplicant)
+can be used together if desired. To do this you need to instruct
+NetworkManager to ignore those interfaces like:
+
+```nix
+{
+  networking.networkmanager.unmanaged = [
+    "*"
+    "except:type:wwan"
+    "except:type:gsm"
+  ];
+}
+```
+
+Refer to the option description for the exact syntax and references to
+external documentation.
+:::