Unknown URLs render raw JSON instead of an application 404 page

[ryanclanigan]

Area

Global routing

Issue:

Opening an unknown app path displays a bare browser JSON document ({"message":"No route found for "no-such-page""}), with no Hidden Boss layout, navigation, recovery link, or user-friendly explanation.

Repro Steps

1. Open /no-such-page.
2. Observe the raw JSON document (unknown-route.png).

Expected

Render a branded 404 page with a link back to the home or leagues page.

Evidence

screenshots/unknown-route.png

[ryanclanigan]

Screenshot evidence: