opencode:rescue hangs in worktrees when run_in_background is used #16

Summary

When opencode:opencode-rescue is dispatched with isolation: "worktree" and the rescue subagent runs its single Bash call with run_in_background: true, the subagent returns immediately. Claude Code sees the subagent exit with no file changes and deletes the worktree — but OpenCode is still running inside the now-deleted directory and hangs indefinitely.

Two paths reach this state today:

1. Explicit: the user includes --background in the rescue request. plugins/opencode/skills/opencode-runtime/SKILL.md:26 and plugins/opencode/agents/opencode-rescue.md:23 treat --background as "Claude-side execution control" without explicitly forbidding run_in_background: true on the Bash call.
2. Implicit: for long prompts, Claude Code sometimes decides to background a slow Bash call on its own.

Suggested fix

Update plugins/opencode/skills/opencode-runtime/SKILL.md and plugins/opencode/agents/opencode-rescue.md to say: strip --background before calling task, and do not set run_in_background on the Bash call. The rescue subagent must wait for OpenCode to complete, because backgrounding in a worktree causes silent orphaning.

Rescue uses opencode-companion task --background for the long-running path already (see handleTask in opencode-companion.mjs:325-342), which spawns a detached worker. That mechanism is the correct way to background OpenCode, not run_in_background on Bash.

Upstream reference

Derived from openai/codex-plugin-cc#198.