Sessions -- sharing, saving, reverting

[lily-de]

Please explain the motivation behind the feature request.
We've received feedback for making sessions:

• shareable - people want to share goose sessions with their team
• findable - people would like to go back to previous sessions
• editable - people would like to be able to jump into a current or former session mid-conversation

With https://github.com/block/goose/pull/1393/files, we are one step closer to being able to have better session management in the UI by removing the vercel sdk fork dependency.

Describe the solution you'd like
This ticket is meant to be a placeholder and this issue will likely be divided up into several smaller sub-issues.

Discussion can be held here or in this discussion topic: #1399

[lily-de]

#1375 (comment)

[baxen]

prototyping at #1417

[spencrmartin]

Linking reference frames for this work for posterity

https://www.figma.com/design/Y55M9mXRyQXjKuTdcBX0GD/Crit-Space?node-id=3007-5514&t=yOOSLWzwyCQ3LLwx-1

[salman1993]

saving & resuming sessions have been implemented & merged:

• feat: sessions api, view & resume prev sessions #1453
• feat: store working directory for sessions  #1559

sharing sessions would be a separate ticket in my mind - we would need a cetralized data store to store the sessions -> started this one: #1572