[beinan]

Summary

• refresh the Lance registry handle before every list, contains, upsert, and remove operation
• use exclusive registry guards in master and server call sites because checkout_latest updates the handle
• add regressions proving master scans and core reads see commits made through another registry handle

Testing

• cargo fmt --all -- --check
• cargo test -p lance-context-core -p lance-context-master -p lance-context-server
• cargo clippy --workspace --all-targets -- -D warnings