Task 214: KaTeX math rendering E2E regression tests

Status: DONE

Description

CLAUDE.md explicitly calls for "TDD-based regression tests to catch and prevent [KaTeX] rendering issues."

Currently zero E2E tests verify math rendering. Add Playwright tests to catch regressions.

Tests

• [ ] KaTeX renders on EP01 (has inline math like `$m \leq ...[ ] KaTeX renders on EP01 (has inline math like )
• [ ] No raw LaTeX syntax leaks into body text
• [ ] Cross-episode summary page has KaTeX rendering
• [ ] Display math ($...$) renders correctly