squash 1.3.0

Parallel renders are now safe: each qmd renders inside an isolated throwaway copy of the quarto project (option squash.isolate_render, TRUE by default), with clean fallback to in-place rendering whenever isolation is not possible. Fixes the random 'Failed to render' errors of concurrent compilation (.quarto crossref corruption, extension resolution races - quarto-dev/quarto-cli#2749). Real error messages are no longer discarded. See NEWS.md and #23.

v1.0.0

First production-ready release