`image_in` is not just the mention switch any more: the table names where each
image-carrying path is gated, and says why the gate exists — a text-only model
answers `[Unsupported Image]`, and a gateway that cannot read image blocks feeds
the model raw base64, which is easy to mistake for a delivered picture.
`doc/images.md` holds the message shape, how `@path` attaches a file, the
per-surface mapping, the provider limits, what a live probe against DeepSeek
confirmed (`tool_result` and `function_call_output` images work, `detail: low`
is 3.4x cheaper, an assistant-message image is a 400), and why the Files API is
not used.
AGENTS.md gets the invariants and the mention/config keys; `doc/architecture.md`
and the example TOML point at it.
NCBM