[FEATURE]: Add quick “last session” switch keybinding #26172

Feature hasn't been suggested before.

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Describe the enhancement you want to request

Description

Currently, switching between sessions requires opening the session list dialog (ctrl-x l), navigating to the desired session, and pressing Enter. This is cumbersome when frequently switching between two sessions. My usual flow is to have two LLMs running at the same time in the same opencode instance.

Proposed Solution

Add a session_last keybinding (o / ctrl-x o) to quickly switch to the previously viewed session, similar to Emacs's C-x o for switching windows.

The feature should:

Track the previous session ID in memory (ephemeral, resets on restart)
Allow instant switching with a single keybind
Only be available when a previous session exists