[FEATURE] Desktop app: option to start with a fresh session instead of resuming the last one

Description

The OpenCode desktop app currently resumes the last session on launch by default. There is no setting to change this behaviour to start with a fresh session instead.

Current behaviour

When launching the desktop app, it restores the most recent session via the handoff entry stored in opencode.global.dat. There is no preference or config option to disable this.

Expected behaviour

A setting (either in the desktop app's preferences UI or in opencode.json/opencode.jsonc) to control launch behaviour:

• Resume last session (current default)
• Start fresh session (new blank chat on every launch)

The CLI/TUI already supports this distinction — opencode starts fresh by default and opencode -c resumes. The desktop app has no equivalent toggle.

Why this matters

Many users prefer starting clean each time and using the session list (/sessions) to resume specific conversations when needed. Auto-resuming the last session can be surprising when the previous session was a one-off task or a long context that shouldn't be carried forward.

Environment

• OpenCode Desktop (Electron)
• macOS 26.2