Greptile Summary

This PR adds a modalities field to the /v1/models extended API response, exposing the supported input/output types (e.g. text, image, audio) for each model. It follows the existing pattern for optional extended fields — omitted by default, included via ?include=modalities or ?include=all.

• openai.go: Adds the Modalities struct, wires it into OpenAIModel, extends the extendedFields list, and safely normalises nil Input/Output slices to []string{} in the conversion path to prevent null arrays in the response.
• openai_retrieve_test.go: Populates Modalities in existing test fixtures, adds assertions for the populated case, and adds a dedicated new test verifying that a ModelCard with a zero-value ModelCardModalities still returns {\"input\":[],\"output\":[]} rather than null.
• Docs: Both English and Chinese API reference pages are updated with the new field description, example JSON, and possible values.

Confidence Score: 5/5

Safe to merge — the change is additive, all nil-slice edge cases are handled, and the new test verifies zero-value behaviour end-to-end.

The conversion code explicitly guards every nil Input/Output slice before constructing the response struct, so the null-array problem that existed for zero-value ModelCardModalities is fully addressed. The new TestOpenAIHandlers_RetrieveModel_ReturnsEmptyModalitiesWhenZeroValue test validates this path end-to-end through the full HTTP handler stack. The change is purely additive (new optional field, omitted by default), so existing callers that do not request modalities are unaffected.

No files require special attention.

Important Files Changed

Sequence Diagram

sequenceDiagram
    participant Client
    participant OpenAIHandlers
    participant parseOpenAIModelInclude
    participant convertModelToOpenAIExtended
    participant ModelCard

    Client->>OpenAIHandlers: "GET /v1/models?include=modalities"
    OpenAIHandlers->>parseOpenAIModelInclude: "includeParam=modalities, defaultIncludeAll=false"
    parseOpenAIModelInclude-->>OpenAIHandlers: "include={modalities:true}, needFullData=true"

    OpenAIHandlers->>convertModelToOpenAIExtended: model, include
    convertModelToOpenAIExtended->>ModelCard: "m.ModelCard != nil?"
    alt ModelCard present
        ModelCard-->>convertModelToOpenAIExtended: Modalities.Input, Modalities.Output
        Note over convertModelToOpenAIExtended: nil slice to []string{}
        convertModelToOpenAIExtended-->>OpenAIHandlers: OpenAIModel with Modalities Input Output
    else ModelCard nil
        convertModelToOpenAIExtended-->>OpenAIHandlers: OpenAIModel Modalities nil omitted
    end

    OpenAIHandlers-->>Client: JSON with modalities input output arrays

_{Reviews (3): Last reviewed commit: "style: fix gci import grouping - testify..." | Re-trigger Greptile}