V10.5 Task A.3: Frontend — Tests for tool call rendering

## Description
Create tests for tool call rendering in frontend.

## Tasks
- [ ] Unit test: render tool_call message
- [ ] Integration test: load history with tool calls
- [ ] E2E test: conversation with tool calls

## Acceptance Criteria
- [ ] 3+ tests created and pass
- [ ] Coverage > 80%

## Related
- Issues: #911, #912 (dependencies)
- Plan: PLAN_V10_5.md