WEB Agentic Allow users to resume/continue previous chat sessions instead of forcing new chat creation

When an agentic chat is stopped, the system automatically starts a "new chat" which loses all context from the previous conversation. This makes it impossible to resume the questions/work that was being done since all previous chat context is lost.

Currently, there doesn't appear to be a way to resume an old chat session.

Users should be able to:

• Resume a previous chat session that was stopped or interrupted
• Continue their work with full context from the previous conversation
• Have a "Stop" button that pauses the chat without losing history (similar to other AI assistants)