DL-484

Agents get two native tools: comms_attach_file (reads a workdir-relative path, reuses an unbound id for the same path and digest, uploads, then posts through the same held and stale handling as comms_post_message) and comms_read_file (an image part only for magic-byte-sniffed PNG/JPEG/GIF/WebP up to 5 MiB, inline UTF-8 text up to 32 KiB, else a saved path outside the git workdir); comms_list_messages renders an attachment as one fenced marker line, and formatDeliversForPrompt renders it unfenced as a known limit

Status: Active (proposed, pending Matt, 2026-10-11)

Record: ../../agent/compass-comms-file-sharing/design.md#d5-agent-tools-attach-and-read