docs(auth): document runtime projection operations

docs/install/examples/thothii-installation.server.yaml

@@ -8,7 +8,13 @@ workspaceRepository:
   branch: main
   access: ssh
 authentication:
-  configDirectory: "/absolute/path/to/thothii-auth"
+  # Root-operated source of truth; it is never mounted into core.
+  configDirectory: "/srv/example/thothii/auth-canonical"
+  runtimeProjection:
+    # The only authentication bind exposed to core by the automatic override.
+    directory: "/srv/example/thothii/auth-runtime"
+    uid: 10001
+    gid: 10001
 overrides:
   - "/absolute/path/to/ThothII/deploy/compose.session-server.yaml.example"
   - "/absolute/path/to/ThothII/deploy/compose.git-ssh.yaml"