Add a 'Clear Chat' button to the chat input area

[alimaandev]

Summary

desktop/src/components/chat/InputBar.tsx handles message input, but there is no way to clear the current conversation from the UI.

Goal

Add a small 'Clear' button in the InputBar (or chat header) that calls an existing onClear/onNewSession handler wired from LeftSidebar/TopBar's session management. Create a new session when clicked.

Tasks

• Add a Clear icon-button with a tooltip in the InputBar
• Wire it to a callback prop; parent component starts a new session
• Guard with a confirm step (window.confirm) to prevent accidental clears
• Add/extend a Vitest test in desktop/src/test/InputBar.test.tsx

Acceptance criteria

• Clicking Clear prompts for confirmation, then starts a new session
• Existing send/voice/gesture behavior unchanged
• Test asserts the button calls the clear handler

Labels

good first issue, help wanted