[Feat] Add custom request fields for OpenAI-compatible providers

[zoomote]

​Created by Roomote. Follow up by mentioning @roomote, in the web UI, or in Discord.

What changed

OpenAI-compatible provider profiles now include a localized Extra Body JSON editor for provider-specific request fields. Zoo Code validates the JSON, rejects runtime-managed and prototype-sensitive keys, persists it only for OpenAI-compatible profiles, and merges safe fields into streaming, non-streaming, O-family, and single-completion requests.

The settings control uses VS Code-themed components, accessible validation feedback, translations for every supported locale, and authoritative visual baselines for dark, light, high-contrast, and high-contrast-light themes.

Why this change was made

Providers such as Sail Research require request-body metadata to select features such as the balanced completion window. Custom headers cannot express those fields, so users previously needed a proxy. This closes #1104.

Impact

Users can configure provider-specific fields such as { "metadata": { "completion_window": "balanced" } } directly in an OpenAI-compatible profile without allowing custom JSON to override Zoo Code's model, messages, tools, streaming, reasoning, temperature, or token limits.

Related PRs

• Zoo-Code-Docs guide: [Docs] Explain OpenAI-compatible custom request fields Zoo-Code-Docs#46

[codecov]

Codecov Report

❌ Patch coverage is 86.66667% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...components/settings/providers/OpenAICompatible.tsx	72.72%	1 Missing and 2 partials ⚠️
webview-ui/src/utils/validate.ts	85.71%	0 Missing and 1 partial ⚠️

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