[FEAT]: Auto-open last workspace + new menu enhancements

[timothycarambat]

What would you like to see?

If I am a user:

And I completed onboarding for the first time or have at least one workspace:

• I am show the empty chat page for the top-most workspace, but it will be augmented with components from #3555 with chat at the bottom that will then all be replaced by chat content on the first chat.

We should also keep track of the last used workspace/thread by a user and auto-open to that, since the top most workspace will not always be the last-used. If this value is known and exists, we bring the user to it.

If the user has no workspaces, they will see the Main page with the same landing content, but they will need to then create a workspace via the sidebar CTA button.

This functionality should not look like page load/redirect spam. It should be seamless and on first load.

[scottybo]

Love this