Feature: Import existing tmux sessions on first launch

[cschanhniem]

Problem

The README shows okena supports dtach, tmux, and screen as session backends for keeping terminals alive across app restarts. Many developers migrating from tmux have years of organized tmux sessions with named windows, pane layouts, and working directories they'd need to recreate manually in okena.

Proposed Feature

Add a tmux import command (or first-launch wizard) that:

1. Reads active tmux sessions via tmux list-sessions and tmux list-windows
2. Creates corresponding okena projects/columns with matching terminal layouts
3. Preserves working directories and window names where possible
4. Handles both attached and detached sessions

Why it fits

Okena already has session persistence (dtach/tmux/screen backends), project columns, and workspace auto-save — the import path just bridges the gap. This would lower the switching cost for tmux power users evaluating okena.

Prior art

• tmuxp (Python) — YAML-based tmux session loader/saver
• tmuxinator — Ruby-based tmux session manager
• Okena's own workspace.json export/import could serve as the target format

Would you consider this? I'm happy to help scope the implementation.