feat(cron): make cron tools opt-in via experimental settings

Change cron/loop tools from opt-out to opt-in. Cron tools are now
disabled by default and can be enabled via:
- settings.json: { "experimental": { "cron": true } }
- Environment variable: QWEN_CODE_ENABLE_CRON=1

This ensures experimental features are explicitly enabled by users
who want to try them.

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

packages/cli/src/config/settingsSchema.ts

@@ -1594,9 +1594,20 @@ const SETTINGS_SCHEMA = {
     category: 'Experimental',
     requiresRestart: true,
     default: {},
-    description: 'Setting to enable experimental features',
+    description: 'Settings to enable experimental features.',
     showInDialog: false,
-    properties: {},
+    properties: {
+      cron: {
+        type: 'boolean',
+        label: 'Enable Cron/Loop Tools',
+        category: 'Experimental',
+        requiresRestart: true,
+        default: false,
+        description:
+          'Enable in-session cron/loop tools (experimental). When enabled, the model can create recurring prompts using cron_create, cron_list, and cron_delete tools. Can also be enabled via QWEN_CODE_ENABLE_CRON=1 environment variable.',
+        showInDialog: true,
+      },
+    },
   },
 } as const satisfies SettingsSchema;