feat: implement extensible plan mode with custom directory configuration

- Adds 'general.plan' configuration object for plan settings (directory).
- Updates 'experimental.plan' to a boolean flag for enablement.
- Implements dynamic high-priority policy for custom plan directories in core.
- Adds migration logic for previous configuration formats.
- Updates documentation and schema.

packages/cli/src/config/config.ts

@@ -833,6 +833,15 @@ export async function loadCliConfig(
     enableExtensionReloading: settings.experimental?.extensionReloading,
     enableAgents: settings.experimental?.enableAgents,
     plan: settings.experimental?.plan,
+    planDirectory:
+      settings.general &&
+      'plan' in settings.general &&
+      typeof settings.general.plan === 'object' &&
+      settings.general.plan !== null &&
+      'directory' in settings.general.plan &&
+      typeof settings.general.plan.directory === 'string'
+        ? settings.general.plan.directory
+        : undefined,
     enableEventDrivenScheduler: true,
     skillsSupport: settings.skills?.enabled ?? true,
     disabledSkills: settings.skills?.disabled,

packages/cli/src/config/settingsSchema.test.ts

@@ -401,6 +401,18 @@ describe('SettingsSchema', () => {
       );
     });
 
+    it('should have plan config in general schema', () => {
+      const setting = getSettingsSchema().general.properties.plan;
+      expect(setting).toBeDefined();
+      expect(setting.type).toBe('object');
+      expect(setting.category).toBe('General');
+      expect(setting.default).toStrictEqual({});
+      expect(setting.requiresRestart).toBe(false);
+      expect(setting.showInDialog).toBe(false);
+      expect(setting.ref).toBe('PlanConfig');
+      expect(setting.description).toBe('Configuration for planning features.');
+    });
+
     it('should have hooksConfig.notifications setting in schema', () => {
       const setting = getSettingsSchema().hooksConfig?.properties.notifications;
       expect(setting).toBeDefined();

packages/cli/src/config/settingsSchema.ts

@@ -266,6 +266,16 @@ const SETTINGS_SCHEMA = {
           },
         },
       },
+      plan: {
+        type: 'object',
+        label: 'Plan Configuration',
+        category: 'General',
+        requiresRestart: false,
+        default: {},
+        description: 'Configuration for planning features.',
+        showInDialog: false,
+        ref: 'PlanConfig',
+      },
       enablePromptCompletion: {
         type: 'boolean',
         label: 'Enable Prompt Completion',
@@ -2131,6 +2141,17 @@ export const SETTINGS_SCHEMA_DEFINITIONS: Record<
       },
     },
   },
+  PlanConfig: {
+    type: 'object',
+    description: 'Planning features configuration.',
+    additionalProperties: false,
+    properties: {
+      directory: {
+        type: 'string',
+        description: 'Custom directory for implementation plans.',
+      },
+    },
+  },
   TelemetrySettings: {
     type: 'object',
     description: 'Telemetry configuration for Gemini CLI.',

packages/cli/src/ui/components/ExitPlanModeDialog.test.tsx

@@ -151,6 +151,7 @@ Implement a comprehensive authentication system with multiple providers.
         ...options,
         config: {
           getTargetDir: () => mockTargetDir,
+          getPlanDirectory: () => mockPlansDir,
           getIdeMode: () => false,
           isTrustedFolder: () => true,
           storage: {
@@ -426,6 +427,7 @@ Implement a comprehensive authentication system with multiple providers.
             useAlternateBuffer,
             config: {
               getTargetDir: () => mockTargetDir,
+              getPlanDirectory: () => mockPlansDir,
               getIdeMode: () => false,
               isTrustedFolder: () => true,
               storage: {

packages/cli/src/ui/components/ExitPlanModeDialog.tsx

@@ -65,7 +65,7 @@ function usePlanContent(planPath: string, config: Config): PlanContentState {
       try {
         const pathError = await validatePlanPath(
           planPath,
-          config.storage.getProjectTempPlansDir(),
+          config.getPlanDirectory(),
           config.getTargetDir(),
         );
         if (ignore) return;
@@ -83,7 +83,7 @@ function usePlanContent(planPath: string, config: Config): PlanContentState {
 
         const result = await processSingleFileContent(
           planPath,
-          config.storage.getProjectTempPlansDir(),
+          config.getPlanDirectory(),
           config.getFileSystemService(),
         );
 

packages/cli/src/ui/components/ToolConfirmationQueue.test.tsx

@@ -45,6 +45,7 @@ describe('ToolConfirmationQueue', () => {
     getModel: () => 'gemini-pro',
     getDebugMode: () => false,
     getTargetDir: () => '/mock/target/dir',
+    getPlanDirectory: () => '/mock/temp/plans',
     getFileSystemService: () => ({
       readFile: vi.fn().mockResolvedValue('Plan content'),
     }),