#4729 GCP Drive files enrichment: download_content can overwrite the state written by upload

In codegen/gcp/enrichments/drive-files.enrich.ts (swamp-club#4449), upload stores the file metadata as state under outputName, else the name global argument, else the Drive file id (line 540). download_content stores the bytes under outputName, else the file id (line 680). Swamp data instance names are not namespaced by spec, so when the model has no name global argument, a download_content after an upload writes the file content under the same instance name as the state and overwrites it; a later get or sync then reads binary content as JSON. The generic media methods added for swamp-club#4450 avoid this by defaulting downloads to media- and refusing an outputName equal to the state instance name; the same approach (a content- prefix default plus the guard) would fix the enrichment. Found during the adversarial review of swamp-club#4450, which left the Drive enrichment unchanged on purpose.