Created new SubagentTool for synchronous subagent execution:
- Implements Tool interface with Name(), Description(), Parameters(), SetContext(), Execute()
- Returns ToolResult with ForUser (summary), ForLLM (full details), Silent=false, Async=false
- Registered in AgentLoop with context support
- Comprehensive test file subagent_tool_test.go with 9 passing tests
Acceptance criteria met:
- ForUser contains subagent output summary (truncated to 500 chars)
- ForLLM contains full execution details with label and result
- Typecheck passes (go build ./... succeeds)
- go test ./pkg/tools -run TestSubagentTool passes (all 9 tests pass)
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>