docs: add peer override example + multi-agent link

docs/concepts/models.md

@@ -23,6 +23,7 @@ Clawdbot selects models in this order:
 Related:
 - `agents.defaults.models` is the allowlist/catalog of models Clawdbot can use (plus aliases).
 - `agents.defaults.imageModel` is used **only when** the primary model can’t accept images.
+- Per-agent defaults can override `agents.defaults.model` via `agents.list[].model` plus bindings (see [/concepts/multi-agent](/concepts/multi-agent)).
 
 ## Quick model picks (anecdotal)