fix(provider): enable image support for custom OpenAI-compatible providers

Custom OpenAI-compatible providers (Ollama, longent, etc.) were unable to
process image attachments because capabilities.input.image defaulted to false.

Now defaults to true for @ai-sdk/openai-compatible providers.

Closes #20802

Author: jwcrystal

packages/opencode/src/provider/provider.ts

@@ -1163,7 +1163,10 @@ const layer: Layer.Layer<
                 input: {
                   text: model.modalities?.input?.includes("text") ?? existingModel?.capabilities.input.text ?? true,
                   audio: model.modalities?.input?.includes("audio") ?? existingModel?.capabilities.input.audio ?? false,
-                  image: model.modalities?.input?.includes("image") ?? existingModel?.capabilities.input.image ?? false,
+                  image:
+                    model.modalities?.input?.includes("image") ??
+                    existingModel?.capabilities.input.image ??
+                    (provider.npm === "@ai-sdk/openai-compatible" ? true : false),
                   video: model.modalities?.input?.includes("video") ?? existingModel?.capabilities.input.video ?? false,
                   pdf: model.modalities?.input?.includes("pdf") ?? existingModel?.capabilities.input.pdf ?? false,
                 },