feat(ui-models): tag the provider rows this deployment declared

A row's stored profile could not tell a hand-declared gateway from a
shipped provider whose models someone narrowed — both look identical from
outside the adapter — so the Models page had no way to mark the routes a
deployment added itself.

The directory entry now carries `declared`, answered by the owning adapter
against its own installed catalog, and the page renders a Custom tag from
it. Absence stays "this adapter draws no such distinction" rather than
"shipped", so a route no adapter claims is labelled neither way.

Also records the default-route work's Agent Note and the e2e evidence for
all three changes: the composer switch writing the section, and the Models
page declaring a route with its own reasoning effort.

packages/host/apiproxy/src/api/llm.ts

@@ -22,6 +22,12 @@ export interface ConfigurableProviderView {
   settingsPath: string[]
   /** Whether the route is currently registered (its models are requestable). */
   active: boolean
+  /**
+   * Whether the owning adapter knows this route only because configuration
+   * declared it. Absent when the adapter draws no such distinction, so a
+   * surface must treat absence as "unknown", not as "shipped".
+   */
+  declared?: boolean
 }
 
 /** Llm-domain unary methods (the map keys llm.* of RpcMethodMap). */