Add MemorySeed model and initial_memories support at three levels:
- POST /workspaces payload: seed memories on workspace creation
- org.yaml workspace config: per-workspace initial_memories with
defaults fallback
- org.yaml global_memories: org-wide GLOBAL scope memories seeded
on the first root workspace during import
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>