This bead asked for implementation of BMC/BDC/EMC marked-content
operators and MarkedContentStack, but these were already fully
implemented in the codebase with comprehensive test coverage.
Verification note documents:
- MarkedContentStack in marked_content_stack.rs
- BMC/BDC/EMC parsers in marked_content_operators.rs
- Integration into execute_with_do in content_stream.rs
- All 6 acceptance criteria covered by passing tests
- 57 marked-content tests all passing
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
