q2-preview: keep task-list checkbox and text on one line (bd-qif9l4cx)

[cscheid]

Summary

A - [x] item in the q2-preview format rendered its checkbox alone on one line with the item text (and the bullet) on the next — seen live on quarto-hub.com on 2026-09-10. Reproduced locally in q2 preview, which shares PreviewRoot with hub-client; every task item was affected, not just nested or mixed lists.

Root cause. TaskItemBody built the <label> around <Node node={Plain}>. The registry's Block entry has been CommentBlock since Comments v1 (#441, which landed nine days after the task-list work in #407); it wraps every commentable block in a positioned <div>. That block box inside the inline <label>, after the <input>, forced the text onto its own line. The attribution wrapper and the measured edit surface are the same class of hazard, so this fix does not depend on bd-q2wqj24c (removing the CommentBlock wrapper).

Fix. Move the <label> into the head block renderer. BulletList/OrderedList provide {checked, onToggle} through a TaskItemContext around the item's head block only; Plain/Para strip the ballot-box marker and render the writer's <label><input type="checkbox"/>…</label> themselves, so every block-level wrapper stays an ancestor of the label. As in the native HTML writer, tight items render li > label and loose items li > p > label — loose (Para-leading) task items previously showed the raw glyph and had no checkbox at all (bd-tvtknbhx polish item 2).

Plan with the full diagnosis and evidence: claude-notes/plans/2026-09-10-q2-preview-task-checkbox-layout.md.

Tests (written red-first)

• ts-packages/preview-renderer task-list integration tests: the label must hold no block element; new fixtures for the reporter's nested/mixed list, a loose list and an ordered list, with toggle coverage for each. 5 failed before the fix, 10/10 after.
• New hub-client e2e spec hub-client/e2e/q2-preview-task-list.spec.ts (real hub + q2-preview iframe): asserts the text's first client rect sits on the checkbox's line. Passes; fails on the pre-fix renderer (toHaveCount(5) received 3).

End-to-end verification

• q2 preview on the reported document after cargo xtask build-q2-preview-spa && cargo build --bin q2: label height 51px → 25.5px, DOM now <li><div …><label><input …>text</label></div></li>; screenshot inspected.
• q2 preview --allow-edit: clicking a checkbox still writes [x]/[ ] back to disk, including for loose items.
• cargo xtask verify --skip-rust-tests green (no Rust source changed).

Closes bd-qif9l4cx. Related: bd-q2wqj24c, bd-tvtknbhx.

🤖 Generated with Claude Code

https://claude.ai/code/session_01RhBKwo1GN35y7fqzL364wB

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