_WSInterceptMiddleware intercepts /ws WebSocket scopes at the outermost
ASGI layer before Starlette routing is consulted, so Mount('/') can never
hand a WS connection to _SPAStaticFiles regardless of route ordering.
Also downgrade the _SPAStaticFiles non-HTTP fallback log from WARNING to
DEBUG — the graceful close still fires as a safety net, but no longer
spams the log since the middleware handles the normal case.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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