feat: implement Watcher subagent for periodic progress monitoring

packages/cli/src/config/config.ts

@@ -990,6 +990,8 @@ export async function loadCliConfig(
     disabledSkills: settings.skills?.disabled,
     experimentalJitContext: settings.experimental?.jitContext,
     experimentalMemoryManager: settings.experimental?.memoryManager,
+    experimentalWatcher: settings.experimental?.watcher,
+    experimentalWatcherInterval: settings.experimental?.watcherInterval,
     contextManagement,
     modelSteering: settings.experimental?.modelSteering,
     topicUpdateNarration: settings.experimental?.topicUpdateNarration,

packages/cli/src/config/settingsSchema.ts

@@ -2217,6 +2217,26 @@ const SETTINGS_SCHEMA = {
           'Enable the experimental Topic & Update communication model for reduced chattiness and structured progress reporting.',
         showInDialog: true,
       },
+      watcher: {
+        type: 'boolean',
+        label: 'Watcher Subagent',
+        category: 'Experimental',
+        requiresRestart: true,
+        default: false,
+        description:
+          'Enable the specialized Watcher subagent for periodic progress monitoring and strategic feedback.',
+        showInDialog: true,
+      },
+      watcherInterval: {
+        type: 'number',
+        label: 'Watcher Interval',
+        category: 'Experimental',
+        requiresRestart: true,
+        default: 20,
+        description:
+          'The number of turns between each Watcher subagent progress review.',
+        showInDialog: true,
+      },
     },
   },
   extensions: {

packages/cli/src/ui/components/messages/__snapshots__/ToolResultDisplay.test.tsx.snap

@@ -21,6 +21,12 @@ exports[`ToolResultDisplay > renders file diff result 1`] = `
 "
 `;
 
+exports[`ToolResultDisplay > renders file diff result 2`] = `
+"
+ No changes detected.
+"
+`;
+
 exports[`ToolResultDisplay > renders nothing for todos result 1`] = `""`;
 
 exports[`ToolResultDisplay > renders string result as markdown by default 1`] = `