SQL generation for the data-migration queue machinery.
All identifier parameters (table, col, shadowName, sourceTable, sourceIdColumn, queueKeyColumn) must be bare, pre-validated SQL identifiers — never user input, never schema-qualified, never quoted. Valid identifiers match [A-Za-z_][A-Za-z0-9_]*. Each method enforces this whitelist up front via SqlIdentifier.validate (same package, no new API) so the documented contract holds mechanically rather than by convention. Implementations interpolate the validated identifiers into DDL/DML as-is.