- Refactor ContentContainer to Vertical layout with fixed header + scrollable content
- Change EnvelopeHeader to ScrollableContainer for long recipient lists
- Parse headers from message content (fixes empty To: field from himalaya)
- Strip all email headers, MIME boundaries, base64 blocks from body display
- Add 22 unit tests for header parsing and content stripping
- Cancelled meeting emails now render with empty body as expected
09d4bc18d7