fix: render unsupported ornamental break fallbacks

[uxjulia]

Summary

• Track when the EPUB parser is inside an ornamental-break container.
• When an empty-alt ornamental image uses an unsupported format, allow the hidden p.ornamental-break-as-text fallback to render instead of being skipped by display: none.
• Add an Unreleased changelog entry for the reader-visible fix.

Root Cause

Some EPUBs provide ornamental breaks as an SVG image plus a hidden text fallback such as * * *. CrossInk does not decode SVG images, but it still honored the CSS that hides the fallback paragraph, so the entire ornamental break disappeared.

Validation

• git diff --check
• pio run -e simulator
• pio run -e default after initializing open-x4-sdk in the fresh worktree