Merge agent and mode into one (#1689)

The concept of mode has been deprecated, there is now only the agent field in the config.

An agent can be cycled through as your primary agent with <tab> or you can spawn a subagent by @ mentioning it. if you include a description of when to use it, the primary agent will try to automatically use it

Full docs here: https://opencode.ai/docs/agents/

packages/sdk/go/internal/requestconfig/requestconfig.go

@@ -133,11 +133,13 @@ func NewRequestConfig(ctx context.Context, method string, u string, body interfa
 	// Fallback to json serialization if none of the serialization functions that we expect
 	// to see is present.
 	if body != nil && !hasSerializationFunc {
-		content, err := json.Marshal(body)
-		if err != nil {
+		buf := new(bytes.Buffer)
+		enc := json.NewEncoder(buf)
+		enc.SetEscapeHTML(true)
+		if err := enc.Encode(body); err != nil {
 			return nil, err
 		}
-		reader = bytes.NewBuffer(content)
+		reader = buf
 	}
 
 	req, err := http.NewRequestWithContext(ctx, method, u, nil)