Files and attachments

Upload documents and media into the owner workspace for the agent to open under approvals.

POST /open-bot/attachments?name=… with raw octet-stream body. Limits: 25 MB docs/images/audio, 200 MB video, six per message, 1 GiB per user. Magic-byte checks; SVG/archives/programs refused. Agent sees paths under /owner/attachments/… as untrusted data.