fix: include is_checked in query context note maps

[careck]

Summary

• note_to_rhai_dynamic was missing the is_checked field, so get_children()/get_note() results always had is_checked undefined
• Views filtering by checkbox state (e.g. task progress counters) got zero matches
• Adds the missing field to match build_note_map which already includes it

Test plan

• All 628 core tests pass
• Import a workspace with checked Task notes, verify is_checked is accessible from views using get_children()