fix: base64 image need clear image url

[zijiren233]

No description provided.

[Copilot]

Pull request overview

This PR improves image b64_json responses by ensuring returned image URLs are omitted when base64 content is present, and enhances usage logging by propagating and recording UsageContext (e.g., resolution/quality/tier) for relevant adaptors.

Changes:

• Clear url fields in image responses when response_format=b64_json and base64 content is successfully produced (OpenAI, SiliconFlow, Ali).
• Propagate UsageContext through adaptor results (Ali + SiliconFlow video handlers) and log it in updateUsageMetrics.
• Normalize Gemini image size values to 1K/2K/4K and update related tests.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
core/relay/controller/dohelper.go	Logs UsageContext fields (resolution/native_resolution/quality/service_tier) into request metrics log entries.
core/relay/controller/dohelper_test.go	Adds coverage ensuring UsageContext fields are included in logged metrics.
core/relay/adaptor/openai/image.go	Clears image url after successful URL→b64_json conversion.
core/relay/adaptor/openai/image_test.go	Adds test asserting url is omitted/empty when b64_json is requested and produced.
core/relay/adaptor/siliconflow/image.go	Clears image url after successful URL→b64_json conversion for SiliconFlow image responses.
core/relay/adaptor/siliconflow/adaptor_test.go	Adds tests for URL clearing in b64_json image responses and verifies video UsageContext propagation.
core/relay/adaptor/siliconflow/video.go	Returns UsageContext (resolution) in video status handler results.
core/relay/adaptor/ali/image.go	Centralizes URL suppression logic for b64_json responses when base64 content is present.
core/relay/adaptor/ali/video.go	Adds UsageContext resolution derivation and improves resolution fallback using stored request metadata when upstream ratio is missing.
core/relay/adaptor/ali/adaptor_test.go	Adds tests for URL clearing in b64_json image responses and stored-resolution fallback + UsageContext resolution on video paths.
core/relay/adaptor/gemini/image.go	Normalizes Gemini image size outputs to 1K/2K/4K (and adjusts downstream token logic accordingly).
core/relay/adaptor/gemini/image_test.go	Updates assertions to match normalized 1K/2K/4K image size outputs.
core/relay/adaptor/vertexai/adaptor_test.go	Updates expected Gemini image conversion payload to use 1K imageSize.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.