fix: improve DOCX Word compatibility

[rogerdigital]

Summary

• Add a DOCX settings part with its relationship and content type so Word can recognize document settings even when the export has no images or links.
• Generate Word-compatible bookmarks for document and heading anchors, and map internal links to the matching bookmarks.
• Register embedded SVG images as image/svg+xml and cover the package structure in regression tests.

Verification

• npm run check:version
• node --test scripts/check-version.test.mjs
• npm run lint:obsidian-warnings
• npm run build
• npm test (430 tests passed)
• Opened a generated DOCX in LibreOffice; its PDF conversion retained an internal link to the heading and rendered the SVG image.

Word for iPad editing still requires device validation.

Refs #94