fix(openwrt): allow opkg-not-found error through RPC sanitizer

"opkg not found at /usr/bin/opkg" was being swallowed by the error
sanitizer and shown as generic "Operation failed". Also fix bare
`opkg list-installed` call in get-status handler to use full path.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

core/archipelago/src/api/rpc/openwrt.rs

@@ -92,7 +92,7 @@ impl RpcHandler {
 
         // TollGate
         let tollgate_installed = router
-            .run("opkg list-installed | grep -q '^tollgate-module-basic-go '")
+            .run("/usr/bin/opkg list-installed | grep -q '^tollgate-module-basic-go '")
             .map(|(_, code)| code == 0)
             .unwrap_or(false);