feat(image-recognition): independent key/url/model defaults

Make the HTTP vision provider's configuration independent of the main chat
model: the API key default moves from DEEPSEEK_API_KEY to IMAGE_RECOGNITION_API_KEY,
and the URL and model get image-recognition-specific defaults (Aliyun DashScope
compatible-mode and qwen3-vl-flash) instead of the chat model's deepseek-v4-flash.
The provider fails loud when no model is configured.

Co-Authored-By: Claude <noreply@anthropic.com>

packages/vision/image-recognition-http/tests/provider.spec.ts

@@ -2,7 +2,6 @@ import { afterEach, describe, expect, it, vi } from 'vitest'
 import type { ImageRecognitionRequest } from '@deepseek-ai/dsh-image-recognition'
 import {
   ImageRecognitionHttpProvider,
-  IMAGE_RECOGNITION_DEFAULT_MODEL,
   type ImageRecognitionHttpProviderOptions,
 } from '../src/provider.ts'
 
@@ -15,7 +14,7 @@ function makeProvider(overrides: Partial<ImageRecognitionHttpProviderOptions> =
   return new ImageRecognitionHttpProvider(() => ({
     resolveApiKey: async () => 'key',
     baseURL: 'https://vision.example.com/v1',
-    model: IMAGE_RECOGNITION_DEFAULT_MODEL,
+    model: 'vision-model',
     maxTokens: 128,
     ...overrides,
   }))
@@ -60,6 +59,11 @@ describe('ImageRecognitionHttpProvider.recognize', () => {
       .rejects.toThrow(expect.objectContaining({ code: 'IMAGE_RECOGNITION_PROVIDER_CREDENTIAL_MISSING' }))
   })
 
+  it('throws IMAGE_RECOGNITION_PROVIDER_CREDENTIAL_MISSING without a model', async () => {
+    await expect(makeProvider({ model: '' }).recognize(request))
+      .rejects.toThrow(expect.objectContaining({ code: 'IMAGE_RECOGNITION_PROVIDER_CREDENTIAL_MISSING' }))
+  })
+
   it('maps a non-2xx response to IMAGE_RECOGNITION_PROVIDER_ERROR', async () => {
     stubFetch({ ok: false, status: 429, json: async () => ({ error: { message: 'rate limited' } }) })
     await expect(makeProvider().recognize(request))