chore: the native token's label follows the active network (closes #372)

networks.js gives each network a nativeCurrency (ETH, SepoliaETH) and nothing
read it: every screen wrote ETH. A nativeCurrency() helper returns the active
network's, and every native balance, value, fee, reserve, type line, history
entry, the contract-recipient warning and the fee-limit refusal use it. The
"ETH" that selectedToken and txInfo.token hold is the native token's id and is
unchanged. A token reporting any network's nativeCurrency is a spoof, as one
reporting ETH already was, and the transaction detail screen calls an entry a
token transfer when it has a token contract, not by its symbol.

Model: opus-5-5

tests/approvalVerify.test.js

@@ -599,6 +599,24 @@ describe("verifySignedTx field comparison", () => {
                 expect(e.message).toContain("1.0 ETH");
             }
         });
+
+        // The fee is in the native currency of the network the transaction is
+        // for, whether its chain id is the hex string the background prepares
+        // or the number ethers parses from a signed transaction.
+        test.each([
+            ["0x1", "ETH"],
+            [1n, "ETH"],
+            ["0xaa36a7", "SepoliaETH"],
+            [11155111n, "SepoliaETH"],
+        ])("the refusal on chain %p names %s", (chainId, nativeCurrency) => {
+            expect(() => assertWithinCeilings({ ...OVER, chainId })).toThrow(
+                "up to 3000.0 " +
+                    nativeCurrency +
+                    ", which is more than the 1.0 " +
+                    nativeCurrency +
+                    " this wallet",
+            );
+        });
     });
 
     test("every field mismatch is a refusal, not a warning", async () => {