[yvos]

Why

A common embedding shows a note read-only and still lets the user tick its checklist, like the preview in most notes apps. With isEditable = false the checkbox click is rejected by shouldChangeText, so today that requires making the whole editor editable.

What changes

allowsTaskCheckboxInteractionWhenReadOnly: Bool (default false). When it is on:

• a checkbox click toggles [ ]/[x] as one undoable edit;
• all other edits stay rejected.

The opt-in native checkbox behavior remains the complete scope of this PR. It does not introduce the separate A2 host-decided activation direction.

This update merges upstream/main at 7c626334d2e87146b0c34e340af3b9bb37a3ba81 with the published topic ancestry intact; the demo conflict retained both the checkbox opt-in and upstream directive completion demo.

Tests

ReadOnlyTaskCheckboxTests covers the default staying off, the opt-in click toggling the binding while ordinary edits stay blocked, the exact three-character mutation, and undo/redo. Full swift test --no-parallel passed 589 core tests in 76 suites and 1 LaTeX test.

The separate host-decided activation proposal remains outside this PR.

[yvos]

Maintainer update: the branch is current through upstream 7c626334 via ordinary merge, retaining the opt-in read-only checkbox behavior with default-off semantics. No A2 host activation was added. Full swift test --no-parallel passed 589 core tests plus 1 LaTeX test. Please re-review the updated head and approve the checks when green.