docs: document full and embedded rendering with server authentication

docs/install/first-start.md

@@ -24,7 +24,7 @@ version control, a URL, or a command line.
 From the repository root, start the interactive setup and select the local profile:
 
 ```sh
-tht setup --profile local
+tht setup --profile local --shell-mode full --shell-default-locale en
 ```
 
 It writes the selected non-secret descriptor below `deploy/<installation-id>/`, the associated
@@ -32,6 +32,18 @@ operator env file, and can create protected secret templates. Keep the descripto
 to commands as `--installation /absolute/path/thothii-installation.yaml` when more than one
 installation can be discovered.
 
+The explicit shell options are important: compatibility defaults without them
+are embedded/en/omics-portal, which expects an Omics document. The Mac's standalone
+installation must use full, with English as its initial locale. Existing browser
+language preferences take precedence over that initial value. Full does not
+configure authentication; setup separately bootstraps local login.
+
+For a server portal, use the [embedded/upstream procedure](authentication-upstream.md)
+instead of creating a second ThothII login. For a standalone server, use full
+with [direct OIDC](authentication-oidc.md). Shell mode does not follow `profile`
+automatically. See [configuration and regeneration](../operations/shell-and-localization.md)
+before modifying an existing installation.
+
 If the descriptor is prepared manually instead, begin with
 [`thothii-installation.local.yaml`](examples/thothii-installation.local.yaml), set mode `0600` or
 `0400`, and ensure `THT_INSTALLATION_CONFIG_SOURCE` in the selected env file points to that exact