Expand slidedeck extension to list current-session decks, versions, and other-session decks

[ladislas]

Summary

Expand the slidedeck extension so it:

• lists slidedecks generated in the current session
• shows versions/iterations for those decks
• also lets users browse slidedecks from unrelated sessions

Motivation

Users need both immediate access to the decks they just generated and a way to revisit older decks from other sessions.

Acceptance Criteria

• The slidedeck extension lists all slidedecks generated in the current session.
• Versions/iterations of current-session slidedecks are visible and distinguishable.
• Users can navigate to slidedecks created in unrelated sessions.
• Current-session decks and other-session decks are clearly distinguishable in the UI.