[cyanzhong]

See MarkEdit-app/MarkEdit#1832.

[Copilot]

🟢 Approval recommended

The focused refactor addresses the reported mismatch with targeted regression coverage and no identified blocking issues.

No open issues 🎉

What changed in this PR

Unifies heading-anchor resolution between preview and hidden-syntax navigation, addressing the punctuation mismatch reported in MarkEdit issue #1832.

Changes:

• Adds shared heading-anchor generation and target lookup.
• Uses the shared lookup in preview navigation and heading-line resolution.
• Adds regression coverage for punctuation, Unicode, duplicate headings, and non-heading targets.

File	Description
tests/​navigation.test.ts	Tests shared heading resolution and preservation of non-heading targets.
tests/​frontMatter.test.ts	Updates expected heading HTML for the new anchor attribute.
src/​render.ts	Registers heading-anchor generation and shares target lookup.
src/​features/​navigation.ts	Uses shared lookup for preview links.
src/​features/​anchors.ts	Implements heading-anchor generation and target resolution.

_{Review effort: Balanced}