feat(dream): add memory dream cli and docs

- New memory/deep-dream.mdx (zh/en/ja): memory flow, distillation rules, dream diary, manual trigger, safety mechanisms
- Simplify long-term memory page, link to deep-dream for details
- New cli/memory-knowledge.mdx (zh/en/ja): memory and knowledge commands
- Move knowledge commands from general.mdx to memory-knowledge.mdx
- Register new pages in docs.json navigation for all languages
- Add /memory dream to cli/index.mdx command tables

docs/cli/general.mdx

@@ -106,45 +106,6 @@ Session: 12 messages | 8 skills loaded
 /logs 50
 ```
 
-## knowledge
-
-查看和管理个人知识库。默认显示知识库统计信息。
-
-```text
-/knowledge
-```
-
-输出示例：
-
-```
-📚 知识库
-
-- 状态：已开启
-- 页面数：12
-- 总大小：45.2 KB
-- 分类明细：
-  - concepts/: 5 篇
-  - entities/: 4 篇
-  - sources/: 3 篇
-```
-
-**查看目录结构：**
-
-```text
-/knowledge list
-```
-
-**开启 / 关闭知识库：**
-
-```text
-/knowledge on
-/knowledge off
-```
-
-<Note>
-  终端 CLI 中 `cow knowledge` 和 `cow knowledge list` 可用，但 `on|off` 仅支持在对话中使用（需实时生效）。
-</Note>
-
 ## version
 
 显示当前 CowAgent 版本号。