Task 405: Add E2E Tests for Episode Transfer Bar Charts

Status: DONE

Summary

Task 394 fixed episode bar chart rendering (they were silently not rendering). Add E2E tests to verify all 5 episodes render their transfer bar charts as SVG elements in the browser.

Rationale

• Bar chart rendering was silently broken before Task 394 — E2E tests prevent regression
• Summary report bar charts already have E2E tests, but episode transfer bar charts don't