[belowzeroff]

Summary

• Reject scalar atoms passed as table columns before row-count inspection.
• Keep vector and list columns supported.
• Add a regression test for the invalid-column case.

User-facing behavior

Before this fix, code such as:

let table = Table::new(&["bad"], &[Value::i64(42)])?;

could proceed with an atom where the Rust API requires a vector or list column. The resulting failure was indirect and depended on the atom payload instead of clearly identifying the invalid column.

Now the constructor fails immediately with an explicit error:

table: column 0 is not a vector or list (type tag ...)

Valid vector and list columns continue to construct tables normally.

Validation

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets -- -D warnings
• RUST_TEST_THREADS=1 cargo test --workspace