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/release-notes/rl-2605.section.md

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+# Release 26.05 (2026.05/??) {#sec-release-26.05}
+
+## Highlights {#sec-release-26.05-highlights}
+
+<!-- To avoid merge conflicts, consider adding your item at an arbitrary place in the list instead. -->
+
+- Create the first release note entry in this section!
+
+## New Modules {#sec-release-26.05-new-modules}
+
+<!-- To avoid merge conflicts, consider adding your item at an arbitrary place in the list instead. -->
+
+- [knot-resolver](https://www.knot-resolver.cz/) in version 6. Available as `services.knot-resolver`. A module for knot-resolver 5 was already available as `services.kresd`.
+
+- [qui](https://github.com/autobrr/qui), a modern alternative webUI for qBittorrent, with multi-instance support. Written in Go/React. Available as [services.qui](#opt-services.qui.enable).
+
+## Backward Incompatibilities {#sec-release-26.05-incompatibilities}
+
+<!-- To avoid merge conflicts, consider adding your item at an arbitrary place in the list instead. -->
+
+- Create the first release note entry in this section!
+
+## Other Notable Changes {#sec-release-26.05-notable-changes}
+
+<!-- To avoid merge conflicts, consider adding your item at an arbitrary place in the list instead. -->
+
+- Create the first release note entry in this section!