-- Remaining Items --
1. CLI status validation in add_* commands (match Session._check pattern)
2. Schema migration system (migrate.py + registry.py load hooks)
3. Blob epoch renewal (WalrusBackend.renew + verity renew CLI command)
4. Async support (WalrusBackend astore/afetch + async MCP tools)
5. MCP structured errors (VerityMCPError + let exceptions propagate naturally)
