Plugin setup errors expose internal stack traces in the TUI

[PanAchy]

Description

When a plugin's setup throws an Error, the Plugins dialog displays the complete internal Effect cause and stack trace. The plugin author's actionable message is buried in framework internals and local paths.

The dialog should show the thrown Error.message with a short diagnostic reference. The complete cause should remain in server logs. This is separate from the import/load diagnostics changed in #46594.

Plugins

None

OpenCode version

V2, reproduced at 956de96d8b8dbb6431cc555bded5a2a84c1f6134 and confirmed unchanged on current v2

Steps to reproduce

1. Create a plugin whose setup throws new Error("Set DEMO_TOKEN before using this plugin").
2. Start OpenCode and open /plugins.
3. Open the failed plugin's details.
4. Observe the full internal stack trace in the dialog.

Screenshot and/or share link

Operating System

Arch Linux (Omarchy)

Terminal

Ghostty