Fix duplicate root route entry in ReceiverUI docs

Removed a redundant entry for the root route (`/`) in the
`ReceiverUI Route Structure` section of the documentation.
Both entries referenced the same file (`Index.razor`) and
served the same purpose, making the duplication unnecessary.

COPILOT_CONTEXT.md

@@ -39,7 +39,7 @@ Client ? API:8088 (YARP Proxy) ? ReceiverUI:52936 (Blazor WASM)
 ### Root Route
 | Route | File | Purpose |
 |---|---|---|
-| `/` | `Index.razor` | Application entry point (landing page). |
+| `/` | `Index.razor` | Application entry point (landing page). | 
 
 ### Sender Routes
 | Route | File | Purpose |