fix(plan): clean up session directories and plans on deletion (#20914)

docs/cli/session-management.md

@@ -121,27 +121,36 @@ session lengths.
 
 ### Session retention
 
-To prevent your history from growing indefinitely, enable automatic cleanup
-policies in your settings.
+By default, Gemini CLI automatically cleans up old session data to prevent your
+history from growing indefinitely. When a session is deleted, Gemini CLI also
+removes all associated data, including implementation plans, task trackers, tool
+outputs, and activity logs.
+
+The default policy is to **retain sessions for 30 days**.
+
+#### Configuration
+
+You can customize these policies using the `/settings` command or by manually
+editing your `settings.json` file:
 
 ```json
 {
   "general": {
     "sessionRetention": {
       "enabled": true,
-      "maxAge": "30d", // Keep sessions for 30 days
-      "maxCount": 50 // Keep the 50 most recent sessions
+      "maxAge": "30d",
+      "maxCount": 50
     }
   }
 }
 ```
 
 - **`enabled`**: (boolean) Master switch for session cleanup. Defaults to
-  `false`.
+  `true`.
 - **`maxAge`**: (string) Duration to keep sessions (for example, "24h", "7d",
-  "4w"). Sessions older than this are deleted.
+  "4w"). Sessions older than this are deleted. Defaults to `"30d"`.
 - **`maxCount`**: (number) Maximum number of sessions to retain. The oldest
-  sessions exceeding this count are deleted.
+  sessions exceeding this count are deleted. Defaults to undefined (unlimited).
 - **`minRetention`**: (string) Minimum retention period (safety limit). Defaults
   to `"1d"`. Sessions newer than this period are never deleted by automatic
   cleanup.