Cross-block annotation highlights not restored on shared URL or draft restore

[backnotprop]

Problem

When an annotation spans multiple blocks (e.g., text selected across two paragraphs), the highlight mark is not visually restored — though the annotation itself appears in the sidebar panel. This affects both shared URL restore and draft restore.

Root Cause

findTextInDOM() in Viewer.tsx searches for the annotation's originalText as a literal string in the DOM. For cross-block selections, originalText contains \n\n characters representing block boundaries. But in the rendered DOM, those boundaries are structural (<p> elements), not text node newlines — so the search fails silently.

The web-highlighter library already captures startMeta/endMeta (DOM path metadata) when annotations are created, and provides highlighter.fromStore(startMeta, endMeta, text, id) for exact restoration. However:

1. toShareable() strips startMeta/endMeta from the compact tuple format
2. fromShareable() leaves them undefined
3. applySharedAnnotations() falls back to text search, which fails for cross-block text

Affected Paths

• Shared URL restore (useSharing.ts → applySharedAnnotations)
• Draft restore (useAnnotationDraft.ts → applySharedAnnotations)

Possible Fixes

1. Include startMeta/endMeta in shareable format — extend the tuple to carry DOM metadata, then use highlighter.fromStore() on restore
2. Fix findTextInDOM() to handle cross-block text — normalize both search text and DOM text to handle structural block boundaries

Option 2 is more robust since it fixes all restore paths without changing the share payload format.

Key Files

• packages/ui/components/Viewer.tsx — findTextInDOM(), applySharedAnnotations()
• packages/ui/utils/sharing.ts — toShareable(), fromShareable()
• packages/ui/types.ts — Annotation.startMeta / endMeta