tui: session becomes stale after restarting opencode

Summary

Restarting opencode leaves the previously active session stale. Continuing requires opening a
new opencode instance, running /session, and manually reattaching to the session.

Environment

• opencode version: opencode2 v0.0.0-next-16197
• OS: Darwin 25.4.0 arm64
• Terminal: tmux (TERM=tmux-256color, COLORTERM=truecolor)
• Shell: /bin/zsh
• Install/channel: next/beta
• Active plugins: Unavailable: omitted at reporter request

Reproduction

1. Open opencode and start or resume a session.
2. Restart opencode.
3. Attempt to continue using the previously active session.
4. Observe that the session is stale.
5. Open a new opencode instance, run /session, and reattach to the original session.

Expected Behavior

After restarting, opencode should restore or reconnect to the active session automatically and
allow it to continue normally.

Actual Behavior

The session becomes stale after restart. The only known workaround is to open a new opencode
instance, run /session, and manually reattach to the original session.

Additional Context

• Workaround: start a new opencode instance and reattach through /session.
• No error output or logs were captured.