UI stuck on 'Thinking...' when tool output is pending #17655

Bug Description

When a tool call completes and returns output (e.g., a question tool with options), the UI sometimes gets stuck showing "Thinking…" indefinitely. The response content is not rendered until the user stops and restarts OpenCode, at which point it appears.

Steps to Reproduce

1. Be in a conversation where the assistant makes a tool call (observed with the question tool specifically)
2. The tool completes and returns output
3. The UI remains stuck on "Thinking…" — no content is displayed
4. Sending a follow-up message ("are you stuck?") does not unstick it
5. Stopping and restarting OpenCode causes the pending output to render

Expected Behavior

Tool output should render in the UI as soon as it's available, not require a restart.

Environment

• Platform: macOS (darwin)
• Observed multiple times across different sessions

Additional Context

The user reports this has happened "a few times," so it's intermittent but reproducible. It may be related to specific tool types (the question tool was involved in this instance) or a general rendering/streaming issue.