MCP screen maps and clearer live terminal screens

Agents can inspect uploaded BMS, MFS, and DDS maps with describe_screen_maps, including fields, tables, PF keys, and MFS messages that use the same field names as the catalog and live session tools. Live screen replies include map= when a screen matches an uploaded map, and list only host styling that differs from the defaults. get_screen_transitions still returns recorded actions that leave a catalog screen.