Environment: Rowboat Mac OS desktop app using Anthropic API

Steps to reproduce:

1. Created an agent workflow that triggers multiple parallel tool calls (e.g., workspace-grep)
2. All tool calls show as "Completed" in the UI
3. On the next turn, the API returns an invalid_request_error

Error message:
"messages.1: tool_use ids were found without tool_result blocks immediately after: [5 tool IDs]. Each tool_use block must have a corresponding tool_result block in the next message."

Expected behavior: Tool results from all completed tool calls should be included in the follow-up message to the API.

Actual behavior: The conversation payload sent to the Anthropic API is missing tool_result blocks for one or more completed tool_use calls, causing a validation error.