feat(knowledge): add cli and update docs

docs/en/cli/general.mdx

@@ -92,6 +92,31 @@ View recent service logs. Shows the last 20 lines by default, up to 50.
 /logs 50
 ```
 
+## knowledge
+
+View and manage the personal knowledge base. Shows statistics by default.
+
+```text
+/knowledge
+```
+
+**View directory structure:**
+
+```text
+/knowledge list
+```
+
+**Enable / disable knowledge base:**
+
+```text
+/knowledge on
+/knowledge off
+```
+
+<Note>
+  In the terminal CLI, `cow knowledge` and `cow knowledge list` are available, but `on|off` is only supported in chat (requires runtime effect).
+</Note>
+
 ## version
 
 Show the current CowAgent version.