Task 394: Add Chart Directive Support to Episode Parser + Validation Tests

Status: DONE

Summary

Tasks 392-393 revealed unsupported directive formats silently fail. Investigation found a BIGGER issue: all 5 episode chart:bar blocks (Tasks 387-391) render as raw YAML text, not charts, because the episode MDX parser doesn't support the chart prefix.

Two-part fix:

1. Add chart directive support to episode MDX parser + rendering pipeline
2. Add comprehensive validation tests to prevent future format mismatches

Rationale

• 5 bar charts across EP01-EP05 are silently broken (showing raw YAML instead of charts)
• Same class of bug as Tasks 392-393 but more widespread
• Validation tests prevent recurrence

Implementation

1. Add chart to episode-mdx-parser.ts fence regex
2. Add bar chart rendering to episode template pipeline (templates.ts)
3. Add comprehensive directive format validation tests
4. Verify all episode bar charts render correctly