feat: add GPT-OSS model family support

[labsclaw]

Summary

Adds support for GPT-OSS models (e.g. gpt-oss-120b-medium) served via the Antigravity Cloud Code API.

Previously, only Claude and Gemini families were recognized — any other model family was silently filtered out as 'unknown' and hidden from the WebUI. This patch adds 'gpt-oss' as a third recognized family.

Changes

• src/constants.js — getModelFamily() returns 'gpt-oss' when model ID contains gpt-oss
• src/cloudcode/model-api.js — isSupportedModel() accepts gpt-oss family (enables /v1/models listing + quota tracking)
• public/js/data-store.js — Frontend getModelFamily() recognizes gpt-oss (no longer defaults to 'other' which means hidden)
• public/views/models.html — Added GPT filter button alongside ALL / CLAUDE / GEMINI (neon-cyan styling)
• public/js/components/model-dropdown.js — Added GPT-OSS group in model selector dropdown

Motivation

Google has begun serving GPT-OSS models (OpenAI open-source) through the Antigravity Cloud Code API alongside Claude and Gemini. Users with Antigravity accounts can now access gpt-oss-120b-medium and similar models, but the proxy rejects them with "Invalid model" because the family filter only recognizes claude and gemini.

Testing

• Verified gpt-oss-120b-medium appears in GET /v1/models response
• Verified successful API call: POST /v1/messages with model: gpt-oss-120b-medium returns 200 OK
• Verified WebUI Models page shows GPT filter button and GPT-OSS quota rows per account

[lunalimadev-sketch]

Hi! 👋 Just checking in on this PR. All CI checks have passed and there are no merge conflicts — looks ready to go.

This feature would unlock GPT-OSS model routing through the proxy, which is a nice addition alongside Claude and Gemini support.

Would love to get this reviewed and merged when someone has a chance. Thanks for the great work! 🚀

[kenny000666]

FYI — I've opened PR #357 (fix: include tool call id for non-Claude, non-Gemini models) which is a companion fix needed for GPT-OSS (and any future non-Gemini model family) to work with tool calls.

The issue: functionCall.id and functionResponse.id are only set for Claude models (isClaudeModel guard). Google Cloud Code API requires these IDs for all models except Gemini (which uses thoughtSignature instead). Without this fix, GPT-OSS models will fail with:

Expected the 'id' of a(n) 'assistant' 'tool_calls' array element to be populated.

The fix changes isClaudeModel → !isGeminiModel in src/format/content-converter.js, which is backwards-compatible and enables tool calls for any new model family.