Updates docs/image-generation.md and skills/image-generation/SKILL.md to
include MiniMax configuration examples, supported aspect ratios, and
troubleshooting references. Also updates the supported provider list to
include minimax alongside openrouter, aihubmix, and gemini.
Adds GeminiImageGenerationClient covering both Imagen 4 (:predict) and
Gemini Flash (:generateContent), wires the gemini ProviderConfig through
the SDK, API server, and gateway entry points, and updates the
image-generation docs and skill. Errors from the Gemini endpoints are
logged and surface with the HTTP status and parsed message instead of an
empty string.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
