Vision model support for Qwen-OAuth (#525)

* refactor: openaiContentGenerator

* refactor: optimize stream handling

* refactor: re-organize refactored files

* fix: unit test cases

* feat: `/model` command for switching to vision model

* fix: lint error

* feat: add image tokenizer to fit vlm context window

* fix: lint and type errors

* feat: add `visionModelPreview` to control default visibility of vision models

* fix: remove deprecated files

* fix: align supported image formats with bailian doc

packages/cli/src/ui/commands/modelCommand.ts

@@ -0,0 +1,88 @@
+/**
+ * @license
+ * Copyright 2025 Qwen
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { AuthType } from '@qwen-code/qwen-code-core';
+import type {
+  SlashCommand,
+  CommandContext,
+  OpenDialogActionReturn,
+  MessageActionReturn,
+} from './types.js';
+import { CommandKind } from './types.js';
+import {
+  AVAILABLE_MODELS_QWEN,
+  getOpenAIAvailableModelFromEnv,
+  type AvailableModel,
+} from '../models/availableModels.js';
+
+function getAvailableModelsForAuthType(authType: AuthType): AvailableModel[] {
+  switch (authType) {
+    case AuthType.QWEN_OAUTH:
+      return AVAILABLE_MODELS_QWEN;
+    case AuthType.USE_OPENAI: {
+      const openAIModel = getOpenAIAvailableModelFromEnv();
+      return openAIModel ? [openAIModel] : [];
+    }
+    default:
+      // For other auth types, return empty array for now
+      // This can be expanded later according to the design doc
+      return [];
+  }
+}
+
+export const modelCommand: SlashCommand = {
+  name: 'model',
+  description: 'Switch the model for this session',
+  kind: CommandKind.BUILT_IN,
+  action: async (
+    context: CommandContext,
+  ): Promise<OpenDialogActionReturn | MessageActionReturn> => {
+    const { services } = context;
+    const { config } = services;
+
+    if (!config) {
+      return {
+        type: 'message',
+        messageType: 'error',
+        content: 'Configuration not available.',
+      };
+    }
+
+    const contentGeneratorConfig = config.getContentGeneratorConfig();
+    if (!contentGeneratorConfig) {
+      return {
+        type: 'message',
+        messageType: 'error',
+        content: 'Content generator configuration not available.',
+      };
+    }
+
+    const authType = contentGeneratorConfig.authType;
+    if (!authType) {
+      return {
+        type: 'message',
+        messageType: 'error',
+        content: 'Authentication type not available.',
+      };
+    }
+
+    const availableModels = getAvailableModelsForAuthType(authType);
+
+    if (availableModels.length === 0) {
+      return {
+        type: 'message',
+        messageType: 'error',
+        content: `No models available for the current authentication type (${authType}).`,
+      };
+    }
+
+    // Trigger model selection dialog
+    return {
+      type: 'dialog',
+      dialog: 'model',
+    };
+  },
+};