[S-05] Professor and student can mark task-like note items complete

[ounold]

Summary

Allow task-like note items to be completed individually, with that state remaining visible in the shared history.

Type

Slice

Status at import

blocked

Why this matters

Completion depends on note-item identity, not just note text. The product must distinguish informational bullets from actionable bullets.

Depends on

• F-01
• S-02
• S-03

Blocked by

• note-item shape and shared update semantics

PRD references

• US-03
• FR-007

Definition of done

• Task-like items can be completed one by one
• Both the professor and the assigned student can update completion state
• Completion remains visible later in the same thread

Notes

• Imported from context/foundation/roadmap.md