feat(core): use claude-3-7-sonnet as basic chat model (#12036)

Close [AI-59](https://linear.app/affine-design/issue/AI-59)

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->

## Summary by CodeRabbit

- **New Features**
  - Added support for two new providers, Anthropic and Exa, in test environments and configurations.
- **Chores**
  - Updated workflow and test environment setup to include API keys for Anthropic and Exa providers.
- **Refactor**
  - Changed the AI model used for the "Chat With AFFiNE AI" prompt to "claude-3-7-sonnet-20250219".

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

.github/workflows/copilot-test.yml

@@ -81,6 +81,8 @@ jobs:
           COPILOT_FAL_API_KEY: ${{ secrets.COPILOT_FAL_API_KEY }}
           COPILOT_GOOGLE_API_KEY: ${{ secrets.COPILOT_GOOGLE_API_KEY }}
           COPILOT_PERPLEXITY_API_KEY: ${{ secrets.COPILOT_PERPLEXITY_API_KEY }}
+          COPILOT_ANTHROPIC_API_KEY: ${{ secrets.COPILOT_ANTHROPIC_API_KEY }}
+          COPILOT_EXA_API_KEY: ${{ secrets.COPILOT_EXA_API_KEY }}
         uses: ./.github/actions/server-test-env
 
       - name: Run server tests
@@ -150,6 +152,8 @@ jobs:
           COPILOT_FAL_API_KEY: ${{ secrets.COPILOT_FAL_API_KEY }}
           COPILOT_GOOGLE_API_KEY: ${{ secrets.COPILOT_GOOGLE_API_KEY }}
           COPILOT_PERPLEXITY_API_KEY: ${{ secrets.COPILOT_PERPLEXITY_API_KEY }}
+          COPILOT_ANTHROPIC_API_KEY: ${{ secrets.COPILOT_ANTHROPIC_API_KEY }}
+          COPILOT_EXA_API_KEY: ${{ secrets.COPILOT_EXA_API_KEY }}
         uses: ./.github/actions/server-test-env
 
       - name: Run Copilot E2E Test ${{ matrix.shardIndex }}/${{ matrix.shardTotal }}