When the user message has at least one ImageContent block, build a
ChatCompletionContentPartUnionParam array with text + image_url
parts instead of the string content path. Image bytes are inlined
as a base64 data URL (data:<media-type>;base64,...). Adjacent text
blocks are merged into a single TextContentPart. Pure-text user
messages stay on the existing string fast path.
This covers OpenAI direct + every openaicompat backend (Ollama,
llama.cpp, llamafile) since they all share the same provider.
Tests: pure text uses OfString; image present emits 2 content parts
(text + image_url with the expected base64 payload); nil-Image
blocks are dropped and adjacent text merges correctly.
vikingowl
c5cc98ed8a