fix: a swap deadline later than a date can hold is stated in words (closes #437)

decode() rendered the Deadline line with toISOString(), which throws on a
date past 275760-09-13, the last a JavaScript date can hold. A later
deadline, such as the uint256 maximum, therefore left the whole swap
undecoded, with nothing saying why. That line now reads
"After 275760-09-13 00:00:00 (no deadline in practice)".

Model: opus-5-5

tests/uniswap.test.js

@@ -554,6 +554,33 @@ describe("uniswap decoder", () => {
         );
     });
 
+    test("shows the deadline as a UTC date and time", () => {
+        const result = uniswap.decode(FIRST_SWAP_CALLDATA, ROUTER_ADDR);
+        expect(detail(result, "Deadline").value).toBe("2026-02-27 08:25:51");
+    });
+
+    // A JavaScript date cannot hold this deadline. It used to make the whole
+    // swap undecoded.
+    test("a deadline of the uint256 maximum is stated in words", () => {
+        const data = buildExecute(
+            "0x08", // V2_SWAP_EXACT_IN
+            [
+                encodeV2SwapExactIn(USER_ADDR, 1000000n, 500000000000000n, [
+                    USDT_ADDR,
+                    WETH_ADDR,
+                ]),
+            ],
+            2n ** 256n - 1n,
+        );
+
+        const result = uniswap.decode(data, ROUTER_ADDR);
+        expect(result).not.toBeNull();
+        expect(result.name).toBe("Swap USDT \u2192 WETH");
+        expect(detail(result, "Deadline").value).toBe(
+            "After 275760-09-13 00:00:00 (no deadline in practice)",
+        );
+    });
+
     test("formats permit amount when not unlimited", () => {
         const data = buildExecute(
             "0x0a",