fix: two pages switching networks no longer lose tracked tokens (closes #701)

A page that had not yet taken another page's network switch could lose
tracked tokens in two ways.

- Its save of an added or removed token wrote its own network's list as
  the new network's list. saveState() now keeps the stored list. It
  makes the add or removal in the list of the page's own network, which
  the stored record keeps in networkTrackedTokens.
- Its own switch in Settings wrote its old lists of tracked tokens per
  network over the stored ones. onChainSwitch() now first takes the
  stored switch with takeStoredNetwork(), as followStoredSettings() does,
  and then switches from there.

Model: opus-5-5

tests/trackedTokensPerNetwork.test.js

@@ -257,6 +257,7 @@ test("a token tracked on Sepolia when another page switched there is not tracked
         ...boot.storage.read("autistmask"),
         networkId: "sepolia",
         trackedTokens: [SEPOLIA_TOKEN],
+        networkTrackedTokens: { mainnet: [] },
     });
 
     await chooseNetwork(boot, "sepolia");
@@ -267,6 +268,103 @@ test("a token tracked on Sepolia when another page switched there is not tracked
     expect(stored.networkTrackedTokens.mainnet).toEqual([]);
 });
 
+// Another popup page saves a switch to Sepolia, where TST is tracked. Before
+// taking that switch, this page adds a token on Ethereum Mainnet. The add's
+// save adds the token to Ethereum Mainnet's list and leaves Sepolia's list as
+// it was.
+test("a token added before this page takes another page's switch is tracked on Ethereum Mainnet", async () => {
+    const boot = await bootOnAddToken("mainnet", {
+        trackedTokens: [MAINNET_TOKEN],
+        networkTrackedTokens: { sepolia: [SEPOLIA_TOKEN] },
+    });
+    expect(boot.pageErrors).toEqual([]);
+    boot.storage.write("autistmask", {
+        ...boot.storage.read("autistmask"),
+        networkId: "sepolia",
+        trackedTokens: [SEPOLIA_TOKEN],
+        networkTrackedTokens: {
+            mainnet: [MAINNET_TOKEN],
+            sepolia: [SEPOLIA_TOKEN],
+        },
+    });
+    const { lookupTokenInfo } = require("../src/shared/balances");
+    lookupTokenInfo.mockResolvedValueOnce({
+        symbol: "NEW",
+        decimals: 18,
+        name: "New Token",
+    });
+
+    boot.node("settings-addtoken-address").value = NEW_TOKEN_ADDRESS;
+    await boot.click("btn-settings-addtoken-manual");
+
+    const stored = boot.storage.read("autistmask");
+    expect(stored.networkId).toBe("sepolia");
+    expect(stored.trackedTokens).toEqual([SEPOLIA_TOKEN]);
+    expect(stored.networkTrackedTokens.mainnet).toEqual([
+        MAINNET_TOKEN,
+        {
+            address: NEW_TOKEN_ADDRESS,
+            symbol: "NEW",
+            decimals: 18,
+            name: "New Token",
+        },
+    ]);
+});
+
+// Another popup page saves a switch to Sepolia, where TST is tracked. Before
+// taking that switch, this page removes DAI on Ethereum Mainnet, as the `[x]`
+// on a tracked token in Settings does. The removal's save drops DAI from
+// Ethereum Mainnet's list and leaves Sepolia's list as it was.
+test("a token removed before this page takes another page's switch is gone from Ethereum Mainnet", async () => {
+    const boot = await bootPopup(
+        unversionedValidProfile({
+            trackedTokens: [MAINNET_TOKEN],
+            networkTrackedTokens: { sepolia: [SEPOLIA_TOKEN] },
+        }),
+    );
+    expect(boot.pageErrors).toEqual([]);
+    boot.storage.write("autistmask", {
+        ...boot.storage.read("autistmask"),
+        networkId: "sepolia",
+        trackedTokens: [SEPOLIA_TOKEN],
+        networkTrackedTokens: {
+            mainnet: [MAINNET_TOKEN],
+            sepolia: [SEPOLIA_TOKEN],
+        },
+    });
+
+    const { state, saveState } = require("../src/shared/state");
+    state.trackedTokens.splice(0, 1);
+    await saveState();
+
+    const stored = boot.storage.read("autistmask");
+    expect(stored.networkId).toBe("sepolia");
+    expect(stored.trackedTokens).toEqual([SEPOLIA_TOKEN]);
+    expect(stored.networkTrackedTokens.mainnet).toEqual([]);
+});
+
+// Another popup page tracks DAI on Ethereum Mainnet and then saves a switch to
+// Sepolia. That switch puts DAI away under Ethereum Mainnet. This page has not
+// taken the switch yet. A switch to Sepolia in this page's Settings keeps DAI
+// on Ethereum Mainnet's list.
+test("a token another page tracked before its own switch stays tracked on Ethereum Mainnet", async () => {
+    const boot = await bootPopup(unversionedValidProfile());
+    expect(boot.pageErrors).toEqual([]);
+    await boot.click("btn-settings");
+    boot.storage.write("autistmask", {
+        ...boot.storage.read("autistmask"),
+        networkId: "sepolia",
+        trackedTokens: [],
+        networkTrackedTokens: { mainnet: [MAINNET_TOKEN] },
+    });
+
+    await chooseNetwork(boot, "sepolia");
+
+    const stored = boot.storage.read("autistmask");
+    expect(stored.networkId).toBe("sepolia");
+    expect(stored.networkTrackedTokens.mainnet).toEqual([MAINNET_TOKEN]);
+});
+
 // Another popup page records a fraud contract on Ethereum Mainnet after this
 // page's last save. The switch to Sepolia drops that fraud contract, as the
 // switch drops this page's own.