Quarto mode for Apex

Apex now has a --mode quarto option aimed at Pandoc/Quarto-style markdown for HTML output. This is not a Quarto replacement — you are not getting cell execution, project rendering, or PDF output from Apex alone. What you do get is a sensible HTML path for .qmd -style documents without running the full Quarto toolchain. Getting started From the command line: apex document.qmd --mode quarto…