Fix provider feature detection to use model.provider, not just URL

Previously, OpenAI-compatible provider settings (like developer role support)
were detected only from the baseUrl. When using custom URLs (e.g., proxies),
detection failed. Now checks model.provider first, then falls back to URL.

Fixes #774

packages/ai/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed OpenAI-compatible provider feature detection to use `model.provider` in addition to URL, allowing custom base URLs (e.g., proxies) to work correctly with provider-specific settings ([#774](https://github.com/badlogic/pi-mono/issues/774))
+
 ## [0.47.0] - 2026-01-16
 
 ### Fixed