/api/v1/environments/{id}/files/{path}

Writes up to 1MB of raw bytes (application/octet-stream) to the normalized

workspace-relative path and returns the digest so clients can verify round-trips.

Principal sessions may write files of their bound environment; the write charges the

principal budget and — unlike environment writes — this face has NO Idempotency-Key

contract, so a network-level retry of the same bytes charges twice (≤ the per-PUT

price; recorded as deviation 15 in the API doc).