[beinan]

Summary

• add shared storage helpers that preserve object-store URIs while joining dataset children and only create directories for local filesystem roots
• keep server and master data roots as URI strings instead of treating them as PathBufs
• validate context and rollout names before create/open/delete so path separators, reserved names, non-portable characters, and overlong names return 400
• document the accepted name format: [A-Za-z0-9_][A-Za-z0-9._-]*, maximum 128 characters, excluding _registry and _stats

Testing

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo test --workspace
• uv run --frozen --extra dev ruff format --check python/
• uv run --frozen --extra dev ruff check python/
• uv run --frozen --extra dev pyright
• .venv/bin/pytest python/tests/ -q (3 passed)

Testing notes

• .codex/skills/ci-pr-helper/scripts/run_ci_checks.sh still references the removed rust/lance-context/Cargo.toml, so the corrected root-workspace commands above were run directly.