[Critical] Fix silent tool failure in background execution

[randomm]

Problem

In packages/opencode/src/core/loop.ts (lines 288-310), if a tool throws in background execution, the error is swallowed and user sees success.

Impact

Users won't know tool failed, leading to confusion and incorrect behavior.

Solution

Ensure error messages reach context as failed task notification. When background task fails:

1. Store error in task result
2. Inject failure notification into next loop iteration
3. Make failure visible to user/agent

Files

• packages/opencode/src/core/loop.ts
• packages/opencode/src/core/tasks.ts

Branch

claude/simplify-agentic-loop-2jRSP

[randomm]

Implemented in branch claude/simplify-agentic-loop-2jRSP. Task failures are now captured with sanitized error messages and injected into context. Failed tasks show status=failed with error field.