Supports {env:NAME} and {file:path} apiKey substitutions in provider config.
Keeps resolved credentials and file contents server-side.
Adds coverage for env and file-based credential resolution.
Uses thinkingLevel for Gemini 3 Flash models
Keeps older Gemini Flash models on thinkingBudget: 0
Updates docs and tests for the new Google request payload
* fix: add support for custom provider base URLs from config
* feat: read custom provider apiKey from config and use it as primary credential when it exists
* doc: update small-model documentation
Jakub Syty