[S-04] Professor and student can update a shared note without losing continuity

[ounold]

Summary

Allow the professor and the assigned student to update an existing note while preserving the thread of what was previously agreed.

Type

Slice

Status at import

blocked

Why this matters

The PRD requires continuity preservation, which is more than a simple overwrite. The product must make post-meeting edits understandable, not merely possible.

Depends on

• F-01
• S-02
• S-03

Blocked by

• explicit continuity model for edits and visible last-edited state

PRD references

• US-04
• FR-006
• FR-008

Definition of done

• Both sides can edit the same note
• The updated state is visible to the professor
• Continuity remains legible when the note is revisited later

Notes

• Imported from context/foundation/roadmap.md