docs(plans): move shipped local-first projects docs to plans/done
KI
4mo ago+0-0
Housekeeping per AGENTS.md rule 6: PR #5731 shipped; its design doc and implementation reference move to plans/done/.
Summary by cubic
Moved the Local-first projects design doc and implementation reference to plans/done now that the project shipped (AGENTS.md rule 6). No content changes; files were only renamed.