feat(libs): create library by name only; root_path derived server-side as BOOKS_DIR/SafeName(name), validated at creation; drop root_path input from admin UI; align changelogs to bilingual template; trim AGENTS.md to rules not derivable from repo layout

docs/CHANGELOG.md

@@ -1,10 +1,16 @@
-# Changelog
+# Changelog / 更新日志
 
-All non-WebUI user-visible changes. Newest version on top.
+All notable non-WebUI user-visible changes should be documented in this file, newest version on top.
+本文件记录所有非 WebUI 的重要用户可见变更，最新版本在最上方。
+
+The format loosely follows Keep a Changelog and can be adapted to the team's habits.
+本文档参考了 Keep a Changelog 的思路，也可以根据团队习惯调整。
 
 ## [Unreleased]
 
-### Changed
+### Changed / 变更
 
+- API: `POST /api/libraries` now takes only `{name}`; `root_path` is generated server-side as `BOOKS_DIR/<sanitized name>` (no client-supplied paths, validated at creation).
+- API：`POST /api/libraries` 只需 `{name}`；`root_path` 由服务端生成为 `BOOKS_DIR/<清洗后的库名>`（不再接受客户端指定路径，创建时即校验）。
 - Repo structure conformed to `AGENTS.md`: `web/` renamed to `frontend/`; backend HTTP layer moved from `internal/api` to `cmd/webui/{api,handlers}` (`cmd/server` → `cmd/webui`); README/CHANGELOGs relocated under `docs/` (`README_zh.md` added as Chinese mirror); module-level `.gitignore`s added (`backend/`, `deploy/`); stray root `library/` removed (book files live in `deploy/api/storage/`); debug binaries untracked.
 - Docs: `docs/README.md` is now the English primary; previous Chinese README mirrored to `docs/README_zh.md`.