fix: a double click on a Top tokens button tracks the token once (closes #729)

A "Top tokens:" button had no already-tracked check and stays enabled until its
save ends, so a fast double click tracked the token twice in memory. Its handler
now checks first. A second click shows "Already tracked." and tracks nothing.
The top 100 dropdown already has this check, so it is unchanged.

Model: opus-5-5

tests/addTokenLateAnswer.test.js

@@ -3,7 +3,9 @@
 // (https://git.eeqj.de/sneak/AutistMask/issues/603). An answer while AddToken
 // still shows goes to AddressDetail. On either add-token screen, an answer for a
 // token tracked while the lookup waited tracks nothing
-// (https://git.eeqj.de/sneak/AutistMask/issues/727). Driven through the real
+// (https://git.eeqj.de/sneak/AutistMask/issues/727). A second click on a "Top
+// tokens:" button tracks nothing
+// (https://git.eeqj.de/sneak/AutistMask/issues/729). Driven through the real
 // popup over a stored profile.
 
 const {
@@ -197,6 +199,8 @@ describe.each([
         await answerSecondClick();
         expect(boot.text("flash-msg")).toBe(alreadyTrackedFlash);
         expect(boot.storage.read("autistmask").trackedTokens).toEqual([TOKEN]);
+        const { state } = require("../src/shared/state");
+        expect(state.trackedTokens).toEqual([TOKEN]);
     });
 
     test("an answer for a token tracked while the lookup waited clears the status line", async () => {
@@ -213,3 +217,44 @@ describe.each([
         expect(state.trackedTokens).toEqual([TOKEN]);
     });
 });
+
+test('a double click on a "Top tokens:" button tracks the token once', async () => {
+    const boot = await bootPopup(
+        unversionedValidProfile({
+            currentView: "address",
+            selectedWallet: 0,
+            selectedAddress: 0,
+        }),
+    );
+    expect(boot.pageErrors).toEqual([]);
+    // The page stub does not turn the markup the screen draws into elements.
+    // So the list hands the screen a stand-in for TOKEN's button.
+    let press;
+    boot.node("settings-addtoken-top10").querySelectorAll = () => [
+        {
+            dataset: {
+                address: TOKEN.address,
+                symbol: TOKEN.symbol,
+                decimals: String(TOKEN.decimals),
+                name: TOKEN.name,
+            },
+            addEventListener: (name, fn) => {
+                press = fn;
+            },
+        },
+    ];
+    await boot.click("btn-settings");
+    await boot.click("btn-settings-add-token");
+
+    const firstClick = press();
+    const secondClick = press();
+    const { state } = require("../src/shared/state");
+    expect(state.trackedTokens).toEqual([TOKEN]);
+    // Read before the first click's save ends, when "Added TST" replaces it.
+    expect(boot.text("flash-msg")).toBe("Already tracked.");
+
+    await Promise.all([firstClick, secondClick]);
+    await boot.settle();
+    expect(state.trackedTokens).toEqual([TOKEN]);
+    expect(boot.storage.read("autistmask").trackedTokens).toEqual([TOKEN]);
+});