ll/gem: implement Gemini Pro 2.5 support

Still to do:
- container support
- sketch.dev support

For #60

Co-Authored-By: sketch <hello@sketch.dev>
diff --git a/llm/gem/gemini/gemini.go b/llm/gem/gemini/gemini.go
index a6b83e4..ab4788c 100644
--- a/llm/gem/gemini/gemini.go
+++ b/llm/gem/gemini/gemini.go
@@ -30,6 +30,7 @@
 
 type Content struct {
 	Parts []Part `json:"parts"`
+	Role  string `json:"role,omitempty"`
 }
 
 // Part is a part of the content.