agent: Support pasting images as context (#29177)

https://github.com/user-attachments/assets/d6a27b05-3590-4f40-a820-f6f99f6bd581

Release Notes:

- agent: Added support for pasting images as context

---------

Co-authored-by: Danilo Leal <daniloleal09@gmail.com>

crates/agent/src/active_thread.rs

@@ -3344,6 +3344,7 @@ pub(crate) fn open_context(
             }),
             cx,
         ),
+        AssistantContext::Image(_) => {}
     }
 }