Support Pi’s max thinking level

[silacode]

RFC

Summary

Add support for Pi’s max thinking level everywhere Flue accepts thinkingLevel.

Background & Motivation

Flue exposes Pi’s thinking-level API, but currently supports only off, minimal, low, medium, high, and xhigh. Newer Pi versions also expose max.

This prevents Flue users from selecting the full reasoning range supported by Pi and compatible models.

Goals

• Allow max anywhere Flue accepts thinkingLevel.
• Keep Flue’s thinking-level type aligned with Pi.
• Support agent defaults and prompt, skill, and task overrides consistently.
• Preserve model- and provider-specific handling of unsupported levels.

Example

import { defineAgent } from '@flue/runtime';

export default defineAgent(() => ({
  model: 'provider/model-id',
  thinkingLevel: 'max',
}));