feat: add Astraflow provider support

[ucloudnb666]

Summary

Adds Astraflow by UCloud as a supported cloud inference provider for the Local Model Provider extension.

Astraflow is an OpenAI-compatible AI model aggregation platform supporting 200+ models, so no new SDK or code changes are required — only configuration.

Changes

package.json

• Description: Updated to mention Astraflow alongside the existing local server list, making it clear the extension also works with cloud OpenAI-compatible endpoints.

• Keywords: Added "astraflow" and "ucloud" so users searching the VS Code Marketplace can discover this extension when looking for Astraflow support.

• serverUrl description: Clarified that the URL field supports cloud providers and linked to Astraflow's website as an example.

• serverPresets default: Added two built-in presets for Astraflow out of the box:

  • Astraflow (Global) → https://api-us-ca.umodelverse.ai/v1 (uses ASTRAFLOW_API_KEY)
  • Astraflow (China) → https://api.modelverse.cn/v1 (uses ASTRAFLOW_CN_API_KEY)

  Users can immediately switch to either endpoint via the "Switch Server Preset" command without manually typing the URL.

How to use Astraflow

1. Sign up at https://astraflow.ucloud-global.com (global) or https://astraflow.ucloud.cn (China) to obtain an API key.
2. In VS Code, run Local Model Provider: Set API Key (Secure) and paste your Astraflow API key.
3. Run Local Model Provider: Switch Server Preset and select Astraflow (Global) or Astraflow (China).
4. The extension will automatically fetch the 200+ available models from Astraflow's endpoint.

Why minimum changes?

Because Astraflow is fully OpenAI-compatible, no new SDK, no new subpackage, and no new source files are needed. The entire integration is a URL + API key, which exactly matches what serverUrl / setApiKey already support.