Escape CSV cells in Markdown tables

[FU-max-boop]

Summary

• escape pipe characters in CSV cells before rendering Markdown tables
• normalize embedded newlines in CSV cells to <br> so a quoted multiline field stays within one table row
• add a focused regression test for pipe and multiline cell content

Tests

• uv run --project packages/markitdown --with pytest python -m pytest packages/markitdown/tests/test_module_misc.py::test_csv_converter_escapes_markdown_table_cells packages/markitdown/tests/test_module_vectors.py::test_convert_stream_with_hints -q
• uv run --project packages/markitdown --with ruff ruff format --check packages/markitdown/src/markitdown/converters/_csv_converter.py packages/markitdown/tests/test_module_misc.py
• uv run --project packages/markitdown --with ruff ruff check packages/markitdown/src/markitdown/converters/_csv_converter.py packages/markitdown/tests/test_module_misc.py
• uv run --project packages/markitdown --with mypy python -m mypy --ignore-missing-imports packages/markitdown/src/markitdown/converters/_csv_converter.py packages/markitdown/tests/test_module_misc.py

[FU-max-boop]

@microsoft-github-policy-service agree