Omnichat button looks like an upload button

Does this issue occur when all extensions are disabled?: Yes

- VS Code Version:
- OS Version:

Steps to Reproduce:

1. Open the Omnichat panel in VS Code.
2. Observe the primary Omnichat action/button in the panel and in the toolbar.
3. The button uses an upload-style icon (paperclip/arrow/upload glyph) which visually reads as an "upload" action rather than opening or starting a chat.

Expected:

- The Omnichat button should have a banner or a different icon. note this icon will be reused for the redesign https://github.com/microsoft/vscode/issues/331350

Actual:

- The current icon looks like an upload action, which is confusing and leads users to think they should attach/upload a file.

Notes:

- This is a UI polish/bug: iconography is misleading and reduces discoverability of Omnichat. Please update the icon to better match chat semantics.

[View original Slack conversation](https://vscodeteam.slack.com/archives/C0B9RD75R6V/p1786990047857849?thread_ts=1786990047.857849&cid=C0B9RD75R6V)