Function is_system_column 

pub fn is_system_column(column_name: &str) -> bool

Check if a column name is a system column.

System columns are virtual columns that are computed at read time and don’t exist in the physical data files. They include:

• _rowid: The row ID
• _rowaddr: The row address
• _rowoffset: The row offset
• _row_last_updated_at_version: The version when the row was last updated
• _row_created_at_version: The version when the row was created

Write paths must reject a stored column named for one: the scanner injects these itself, so a stored copy collides with the injected one on read.