fix(web): list nesting ignores markers inside multiline mention chips

Tab and empty-item Enter scanned physical lines above the cursor, so a
numbered line inside a multiline @"..." chip read as a list parent.
listMarkersAbove now joins lines that a chip spans, matching the forward
renumber scan.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
53ba38bb47Julius Marminge committed on 10/22/2026, 7:37:51 PMparent1fc61c6
2 files changedLine totals unavailable