Archive completed workflow changes

Archive completed change and sync delta specs to main

Formal closure of a workflow change with audit trail and optional spec propagation to main

• · change name (optional, inferred)
• · artifact completion status
• · delta spec diffs

• · archived change directory (YYYY-MM-DD-<name>)
• · synced main specs (optional)

• · openspec CLI
• · openspec-sync-specs skill
• · git

• · all tasks complete (warning if not)
• · all artifacts done (warning if not)

• · archive dir already exists
• · user declines sync without confirmation
• · change locked by user edit
• · delta spec sync fails

• · timestamp-based archive naming
• · explicit warnings for incomplete work
• · offers sync+archive as atomic option
• · generates dated summary