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.

docs/core-data-structures/core.md

@@ -313,6 +313,15 @@ interface LlmConfigurableProvider {
    * object; empty when the whole section is the profile.
    */
   settingsPath: readonly string[]
+  /**
+   * Whether the owning adapter knows this route only because configuration
+   * declared it — a gateway or self-hosted server it ships nothing about.
+   * Absent means the adapter draws no such distinction; false means it does
+   * and this route is one of its own. Only the adapter can answer: a stored
+   * profile is how a user-added route AND a corrected shipped one both look
+   * from outside.
+   */
+  declared?: boolean
 }
 ```