* feat(table-catalog): complete namespace REST contracts * fix(table-catalog): simplify namespace existence guard * fix(table-catalog): restore migration guard coverage * fix(table-catalog): preserve encoded namespace segments * fix(table-catalog): reject implicit namespace creates Co-Authored-By: heihutu <[email protected]> --------- Co-authored-by: Henry Guo <[email protected]> Co-authored-by: houseme <[email protected]> Co-authored-by: heihutu <[email protected]>