GET /clipboard/entries/:id/file

Serves the bytes of an entry's first materialized free-file (ADR-008 P5-1b). The daemon materializes inbound free-files into a controlled cache and rewrites the entry's file-list representation; this endpoint reads that cached file and streams it back. Binary endpoint: the response is application/octet-stream (the representation MIME when known), NOT the { data, ts } JSON envelope (ADR-008 §0.2 keeps binary endpoints exempt). A Content-Disposition: attachment header carries the cached filename so CLI recv can name the local copy. Returns 404 when the entry is unknown or carries no materialized free-file, 500 on a read failure.