Add tabbed sessions and keyboard shortcuts to navigate between them

[mshostack]

Validations

• [X] I believe this is a way to improve. I'll try to join the Continue Discord for questions
• [ ] I'm not able to find an open issue that requests the same enhancement

Problem

When using Continue to generate a list of tasks or high-level outline of something I then want to dive deeper on, I want the ability to create a new session tab(s) to preserve the context and accessibility of the previous response without having to use "Last Session" which is limiting and clunky.

Solution

1. These tabs should be created using a button or keyboard shortcut
2. The initial tab I'm on that I want to preserve should add a little onHover button similar to what appears when you mouseover a codeblock, but instead of options to run in terminal, insert, or copy, it should let me either: a. Start a new tab session using the selected text (which may include just text or other formatted items like codeblocks) b. Enter a new starting prompt for the new tab, and then insert the selected text/context below it. Think "Create a detailed step by step approach for implementing the below step from a refactoring plan"