Resolve conflicts at shared registration points by unioning both features
(footnotes + the already-merged html-embed / page-embed work):
- slash-menu/menu-items.ts, editor extensions.ts: keep both imports + configures
- collaboration.util.ts: register footnote nodes and pageEmbed
- editor-ext marked.utils.ts: register footnote + html-embed markdown extensions
- editor-ext package.json/tsconfig.json/vitest.config.ts: union of test config
(jsdom env for footnote DOM tests + combined test/spec include glob)
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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