Simple tabs for sessions & fork

[ferenci84]

Validations

• 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

Scenario 1: I usually have a main session, then I have a standalone coding question I want to ask.
Scenario 2: I want to copy things from the old session into a new one and switch between them
Scenario 3: For whatever other reason I want to keep more than one session to be opened

A more advanced scenario:
Scenario 4: I have a history, and want to start a series of questions that is related to the current session, but I want to keep the current one for reference.

Solution

Simple tabs feature should be added. This would support scenario 1-3

I believe it would also be simpe to add fork feature (in a form of action button at the end of an assistant response, just like copy or delete). This would support scenario 4.

Some other extensions already implemented this and I found them very helpful:

The branch feature is included in many standalone AI chat application:

Note: In those applications you commonly don't have tabs, but you have an always-visible sidebar containing history similar to one in Continue. Continue also have a sidebar like that, but it's always-visible only if you enlarge the window:

Related to these issues:
#774
#1858

I believe tabs would solve this too:
#3468

[ferenci84]

I created a PR for the tabs feature: #4051

I was using it for a while with my work, and it's working almost good, I noticed few minor things though. I'll make an update in few days.

[ferenci84]

I have made an update to the PR, now it aligns more to the theme colors, and I corrected few minor bugs.