Append a single column to a workspace's table schema. Position is auto-computed as next-after-max so the contiguity invariant holds. Key collision (409) if a column with the same key already exists. Editor role required. Use this for per-column additions; use get_workspace_schema + update_workspace_columns (PUT on /columns) for full schema replacement or reordering. Multi-surface workspaces accept `surface_slug` to target a specific table sheet (use `list_surfaces` to enumerate); omit to fall through to the workspace's primary table surface.
Connector