docs(local-model): the models on this Mac, add, switch and delete

The guide, the API reference, the invariants and the two CLAUDE files
describe the library with one model in use: the state file's list, the
three verbs and their refusals, the two cached listings of the view, and
the window's list with its row actions.

Co-Authored-By: Claude Fable 5.2 <noreply@anthropic.com>

docs/wiki/Custom-Model-Endpoints.md

@@ -234,6 +234,11 @@ Good to know:
   but it is changed and removed in the local model window, not here.
 - Codeman starts the runtime with the server and stops it with it. **Stop** keeps it from
   starting next time.
+- More than one model can be on the Mac, and one of them runs at a time. Once a model is
+  installed the window lists the models with what each takes on disk: **Add a model**
+  downloads another one, **Use** switches to a model that is already there (nothing is
+  downloaded; close the sessions on the model first), and **Delete** removes one, after one
+  question. The model in use cannot be deleted: switch first, or use **Remove**.
 - **Remove** deletes the runtime and the endpoint, and the model too if you tick that. The
   coding agent stays installed.
 - If the model on disk is no longer the one that was installed, Codeman refuses to start a