feat(provider): add FriendliAI provider support

[minpeter]

Summary

Add native support for FriendliAI as an OpenAI-compatible provider with proper handling of Friendli-specific features.

Changes

transform.ts

1. variants() - Returns empty object for Friendli provider

   • Friendli uses chat_template_kwargs instead of reasoningEffort
   • Variants are defined explicitly via config or models.dev

2. providerOptions() - Adds Friendli-specific provider options

   • Strips unsupported thinking option
   • Injects parse_reasoning: true for backward compatibility with pre-Dec 2025 models

3. schema() - Sanitizes JSON Schema for Friendli constraints

   • Removes unsupported properties: minLength, maxLength (string), minimum/maximum (number only)
   • Filters unsupported formats (only uuid, date-time, date, time allowed)
   • Removes maxItems, clamps minItems > 1 to 1
   • Removes unsupported composition: allOf, oneOf, not (only anyOf supported)
   • Removes additionalProperties
   • Based on: https://friendli.ai/docs/guides/structured-outputs

Related

• models.dev PR: (will be linked after creation)

Testing

Tested with local build against FriendliAI serverless endpoints:

• ✅ Qwen3-32B with --variant off/on
• ✅ K-EXAONE-236B-A23B with --variant off/on
• ✅ GLM-4.6 with --variant off/on