fix: add fallback popup window for tx and sign approval requests (closes #4)

requestTxApproval and requestSignApproval were missing the
openApprovalWindow fallback that requestApproval (connection
requests) already had. When chrome.action.openPopup() fails
(which it does when not triggered by a user gesture in MV3),
no popup appeared — the user had to manually click the toolbar
icon to find the confirmation screen.

Now all three approval types use the same pattern: try
openPopup() first, fall back to a centered standalone window.

src/background/index.js

@@ -148,7 +148,7 @@ function requestApproval(origin, hostname) {
 }
 
 // Open a tx-approval popup and return a promise that resolves with txHash or error.
-// Uses the toolbar popup only — no fallback window.
+// Tries the toolbar popup first, falls back to a standalone window.
 function requestTxApproval(origin, hostname, txParams) {
     return new Promise((resolve) => {
         const id = crypto.randomUUID();
@@ -160,27 +160,26 @@ function requestTxApproval(origin, hostname, txParams) {
             type: "tx",
         };
 
-        if (actionApi && typeof actionApi.setPopup === "function") {
+        if (actionApi && typeof actionApi.openPopup === "function") {
             actionApi.setPopup({
                 popup: "src/popup/index.html?approval=" + id,
             });
-        }
-        if (actionApi && typeof actionApi.openPopup === "function") {
             try {
                 const result = actionApi.openPopup();
                 if (result && typeof result.catch === "function") {
-                    result.catch(() => {});
+                    result.catch(() => openApprovalWindow(id));
                 }
             } catch {
-                // openPopup unsupported — user clicks toolbar icon
+                openApprovalWindow(id);
             }
+        } else {
+            openApprovalWindow(id);
         }
     });
 }
 
 // Open a sign-approval popup and return a promise that resolves with { signature } or { error }.
-// Uses the toolbar popup only — no fallback window.  If openPopup() fails the
-// popup URL is still set, so the user can click the toolbar icon to respond.
+// Tries the toolbar popup first, falls back to a standalone window.
 function requestSignApproval(origin, hostname, signParams) {
     return new Promise((resolve) => {
         const id = crypto.randomUUID();
@@ -192,20 +191,20 @@ function requestSignApproval(origin, hostname, signParams) {
             type: "sign",
         };
 
-        if (actionApi && typeof actionApi.setPopup === "function") {
+        if (actionApi && typeof actionApi.openPopup === "function") {
             actionApi.setPopup({
                 popup: "src/popup/index.html?approval=" + id,
             });
-        }
-        if (actionApi && typeof actionApi.openPopup === "function") {
             try {
                 const result = actionApi.openPopup();
                 if (result && typeof result.catch === "function") {
-                    result.catch(() => {});
+                    result.catch(() => openApprovalWindow(id));
                 }
             } catch {
-                // openPopup unsupported — user clicks toolbar icon
+                openApprovalWindow(id);
             }
+        } else {
+            openApprovalWindow(id);
         }
     });
 }