[Bug] Image paste auto-inserts placeholder text when only image is sent

Bug Description
if you alt+v an image into chat and hit enter, it automatically adds the placeholder text. Most often I don't want to do that since I'm pasting as a response to a fix or answering a request from claude. It seems it should not place any text in the response if you paste a screenshot and just hit enter.

Environment Info

• Platform: win32
• Terminal: windows-terminal
• Version: 2.0.76
• Feedback ID: ddd59bf7-15de-44c4-bbd4-0f3cf74e2e8b